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    <link:label id="lab_ngs_LineOfCreditFacilityPotentialIncreaseInBorrowingCapacity_815E0D7CAF753672DF64BD21F1E60B77_label_en-US" xlink:label="lab_ngs_LineOfCreditFacilityPotentialIncreaseInBorrowingCapacity_815E0D7CAF753672DF64BD21F1E60B77" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Potential Increase in Borrowing Capacity</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityPotentialIncreaseInBorrowingCapacity_815E0D7CAF753672DF64BD21F1E60B77_documentation_en-US" xlink:label="lab_ngs_LineOfCreditFacilityPotentialIncreaseInBorrowingCapacity_815E0D7CAF753672DF64BD21F1E60B77" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Potential Increase in Borrowing Capacity</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineOfCreditFacilityPotentialIncreaseInBorrowingCapacity" xlink:label="loc_ngs_LineOfCreditFacilityPotentialIncreaseInBorrowingCapacity_815E0D7CAF753672DF64BD21F1E60B77" xlink:type="locator" />
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    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivable_841542413183CBF6C0F3BD21F1E60F6C_terseLabel_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivable_841542413183CBF6C0F3BD21F1E60F6C" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowing base, component, % of eligible accounts receivable</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivable_841542413183CBF6C0F3BD21F1E60F6C_label_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivable_841542413183CBF6C0F3BD21F1E60F6C" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity, Component, Percentage of Eligible Accounts Receivable</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivable_841542413183CBF6C0F3BD21F1E60F6C_documentation_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivable_841542413183CBF6C0F3BD21F1E60F6C" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity, Component, Percentage of Eligible Accounts Receivable</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivable" xlink:label="loc_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleAccountsReceivable_841542413183CBF6C0F3BD21F1E60F6C" xlink:type="locator" />
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    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleGeneralInventory_B5FCA4F96092D4361B4CBD21F1E63CA4_terseLabel_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleGeneralInventory_B5FCA4F96092D4361B4CBD21F1E63CA4" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowing base, component, % of eligible inventory</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleGeneralInventory_B5FCA4F96092D4361B4CBD21F1E63CA4_label_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleGeneralInventory_B5FCA4F96092D4361B4CBD21F1E63CA4" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity, Component, Percentage of Eligible General Inventory</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleGeneralInventory_B5FCA4F96092D4361B4CBD21F1E63CA4_documentation_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleGeneralInventory_B5FCA4F96092D4361B4CBD21F1E63CA4" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity, Component, Percentage of Eligible General Inventory</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleGeneralInventory" xlink:label="loc_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleGeneralInventory_B5FCA4F96092D4361B4CBD21F1E63CA4" xlink:type="locator" />
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    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56_terseLabel_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowing base, allowable share of total commitment amount attributable to inventory component</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56_label_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity, Allowable Share of Total Commitment Amount Attributable to General Inventory Component</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56_documentation_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity, Allowable Share of Total Commitment Amount Attributable to General Inventory Component</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent" xlink:label="loc_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56" xlink:to="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityAllowableShareOfTotalCommitmentAmountAttributableToGeneralInventoryComponent_F9EA8FB9E2C0F80EC856BD21F1E6EB56" xlink:type="arc" />
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684_terseLabel_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowing base, component, % of eligible equipment inventory</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684_label_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity, Component, Percentage of Eligible Equipment Inventory</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684_documentation_en-US" xlink:label="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity, Component, Percentage of Eligible Equipment Inventory</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory" xlink:label="loc_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684" xlink:to="lab_ngs_LineOfCreditFacilityCurrentBorrowingCapacityComponentPercentageOfEligibleEquipmentInventory_0306005E3B8AF6E55C5FBD21F1E62684" xlink:type="arc" />
    <link:label id="lab_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_3AF83045A9CC4C3D8946BD21F1E68495_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_3AF83045A9CC4C3D8946BD21F1E68495" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Borrowing base amount available</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_3AF83045A9CC4C3D8946BD21F1E68495_label_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_3AF83045A9CC4C3D8946BD21F1E68495" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Current Borrowing Capacity</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_3AF83045A9CC4C3D8946BD21F1E68495" xlink:type="locator" />
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    <link:label id="lab_ngs_LineOfCreditFacilityReferenceRateNumberOfAllowableBorrowingsOutstanding_83E5379B8A26BADF0363BD21F1E79EFE_terseLabel_en-US" xlink:label="lab_ngs_LineOfCreditFacilityReferenceRateNumberOfAllowableBorrowingsOutstanding_83E5379B8A26BADF0363BD21F1E79EFE" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Reference rate, number of allowable LIBOR-based borrowings outstanding</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityReferenceRateNumberOfAllowableBorrowingsOutstanding_83E5379B8A26BADF0363BD21F1E79EFE_label_en-US" xlink:label="lab_ngs_LineOfCreditFacilityReferenceRateNumberOfAllowableBorrowingsOutstanding_83E5379B8A26BADF0363BD21F1E79EFE" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Reference Rate, Number of Allowable Borrowings Outstanding</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityReferenceRateNumberOfAllowableBorrowingsOutstanding_83E5379B8A26BADF0363BD21F1E79EFE_documentation_en-US" xlink:label="lab_ngs_LineOfCreditFacilityReferenceRateNumberOfAllowableBorrowingsOutstanding_83E5379B8A26BADF0363BD21F1E79EFE" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Reference Rate, Number of Allowable Borrowings Outstanding (e.g. LIBOR Rate, CB Floating Rate, etc.)</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineOfCreditFacilityReferenceRateNumberOfAllowableBorrowingsOutstanding" xlink:label="loc_ngs_LineOfCreditFacilityReferenceRateNumberOfAllowableBorrowingsOutstanding_83E5379B8A26BADF0363BD21F1E79EFE" xlink:type="locator" />
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    <link:label id="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_66161942AC509A168D36BD21F1E7481A_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_66161942AC509A168D36BD21F1E7481A" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Variable rate, applicable margin</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_66161942AC509A168D36BD21F1E7481A_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_66161942AC509A168D36BD21F1E7481A" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Basis Spread on Variable Rate</link:label>
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    <link:label id="lab_ngs_LineofCreditFacilityCommitmentCoverageRatio_0E30E5C919236BF22352BD21F1E72F9B_terseLabel_en-US" xlink:label="lab_ngs_LineofCreditFacilityCommitmentCoverageRatio_0E30E5C919236BF22352BD21F1E72F9B" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Minimum commitment coverage ratio allowed</link:label>
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    <link:label id="lab_ngs_LineofCreditFacilityCommitmentCoverageRatio_0E30E5C919236BF22352BD21F1E72F9B_documentation_en-US" xlink:label="lab_ngs_LineofCreditFacilityCommitmentCoverageRatio_0E30E5C919236BF22352BD21F1E72F9B" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Minimum Commitment Coverage Ratio Allowed</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineofCreditFacilityCommitmentCoverageRatio" xlink:label="loc_ngs_LineofCreditFacilityCommitmentCoverageRatio_0E30E5C919236BF22352BD21F1E72F9B" xlink:type="locator" />
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    <link:label id="lab_ngs_LineofCreditFacilityLeverageRatio_373BB3C262071A999A1EBD21F1E76A35_terseLabel_en-US" xlink:label="lab_ngs_LineofCreditFacilityLeverageRatio_373BB3C262071A999A1EBD21F1E76A35" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Maximum leverage ratio allowed</link:label>
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    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineofCreditFacilityLeverageRatio" xlink:label="loc_ngs_LineofCreditFacilityLeverageRatio_373BB3C262071A999A1EBD21F1E76A35" xlink:type="locator" />
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    <link:label id="lab_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D_terseLabel_en-US" xlink:label="lab_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Default trigger, certain defaults of other company indebtedness, amount</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D_label_en-US" xlink:label="lab_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Default Trigger, Certain Defaults of Other Company Indebtedness, Amount</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D_documentation_en-US" xlink:label="lab_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Default Trigger, Certain Defaults of Other Company Indebtedness, Amount</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount" xlink:label="loc_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D" xlink:to="lab_ngs_LineOfCreditFacilityDefaultTriggerCertainDefaultsOfOtherCompanyIndebtednessAmount_78999FF055EE785C11C0BD21F1E78C6D" xlink:type="arc" />
    <link:label id="lab_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73_terseLabel_en-US" xlink:label="lab_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Default trigger, rendering of certain judgments, amount</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73_label_en-US" xlink:label="lab_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Default Trigger, Rendering of Certain Judgments, Amount</link:label>
    <link:label id="lab_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73_documentation_en-US" xlink:label="lab_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Default Trigger, Rendering of Certain Judgments, Amount</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount" xlink:label="loc_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73" xlink:to="lab_ngs_LineOfCreditFacilityDefaultTriggerRenderingOfCertainJudgmentsAmount_5BC3196C31DDDE46394DBD21F1E78D73" xlink:type="arc" />
    <link:label id="lab_us-gaap_LinesOfCreditCurrent_A493FBE503F5EFEE0EBBBD21F1E7E046_terseLabel_en-US" xlink:label="lab_us-gaap_LinesOfCreditCurrent_A493FBE503F5EFEE0EBBBD21F1E7E046" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Line of credit</link:label>
    <link:label id="lab_us-gaap_LinesOfCreditCurrent_A493FBE503F5EFEE0EBBBD21F1E7E046_label_en-US" xlink:label="lab_us-gaap_LinesOfCreditCurrent_A493FBE503F5EFEE0EBBBD21F1E7E046" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit, Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LinesOfCreditCurrent" xlink:label="loc_us-gaap_LinesOfCreditCurrent_A493FBE503F5EFEE0EBBBD21F1E7E046" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LinesOfCreditCurrent_A493FBE503F5EFEE0EBBBD21F1E7E046" xlink:to="lab_us-gaap_LinesOfCreditCurrent_A493FBE503F5EFEE0EBBBD21F1E7E046" xlink:type="arc" />
    <link:label id="lab_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_7974D321FA06B66BE7C1BD21F1E7D4A1_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_7974D321FA06B66BE7C1BD21F1E7D4A1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Weighted average interest rate</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_7974D321FA06B66BE7C1BD21F1E7D4A1_label_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_7974D321FA06B66BE7C1BD21F1E7D4A1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Interest Rate During Period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_7974D321FA06B66BE7C1BD21F1E7D4A1" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_7974D321FA06B66BE7C1BD21F1E7D4A1" xlink:to="lab_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_7974D321FA06B66BE7C1BD21F1E7D4A1" xlink:type="arc" />
    <link:label id="lab_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_CF84A966E489975DF0BEBD21F2008DC9_terseLabel_en-US" xlink:label="lab_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_CF84A966E489975DF0BEBD21F2008DC9" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock-Based Compensation</link:label>
    <link:label id="lab_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_CF84A966E489975DF0BEBD21F2008DC9_label_en-US" xlink:label="lab_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_CF84A966E489975DF0BEBD21F2008DC9" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Disclosure of Compensation Related Costs, Share-based Payments [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:label="loc_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_CF84A966E489975DF0BEBD21F2008DC9" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_CF84A966E489975DF0BEBD21F2008DC9" xlink:to="lab_us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_CF84A966E489975DF0BEBD21F2008DC9" xlink:type="arc" />
    <link:label id="lab_us-gaap_AssetsAbstract_C450DD11878BEE1284650EEB4041BF85_terseLabel_en-US" xlink:label="lab_us-gaap_AssetsAbstract_C450DD11878BEE1284650EEB4041BF85" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">ASSETS</link:label>
    <link:label id="lab_us-gaap_AssetsAbstract_C450DD11878BEE1284650EEB4041BF85_label_en-US" xlink:label="lab_us-gaap_AssetsAbstract_C450DD11878BEE1284650EEB4041BF85" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Assets [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="loc_us-gaap_AssetsAbstract_C450DD11878BEE1284650EEB4041BF85" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AssetsAbstract_C450DD11878BEE1284650EEB4041BF85" xlink:to="lab_us-gaap_AssetsAbstract_C450DD11878BEE1284650EEB4041BF85" xlink:type="arc" />
    <link:label id="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue_C063604C1536A72AB6020EEB40416E19_terseLabel_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue_C063604C1536A72AB6020EEB40416E19" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Cash and cash equivalents</link:label>
    <link:label id="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue_C063604C1536A72AB6020EEB40416E19_label_en-US" xlink:label="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue_C063604C1536A72AB6020EEB40416E19" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash and Cash Equivalents, at Carrying Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_C063604C1536A72AB6020EEB40416E19" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_C063604C1536A72AB6020EEB40416E19" xlink:to="lab_us-gaap_CashAndCashEquivalentsAtCarryingValue_C063604C1536A72AB6020EEB40416E19" xlink:type="arc" />
    <link:label id="lab_us-gaap_AccountsReceivableNetCurrent_00617EEDC3E023C9454F0EEB40422BF5_terseLabel_en-US" xlink:label="lab_us-gaap_AccountsReceivableNetCurrent_00617EEDC3E023C9454F0EEB40422BF5" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Trade accounts receivable, net of allowance for doubtful accounts of $507 and $436, respectively</link:label>
    <link:label id="lab_us-gaap_AccountsReceivableNetCurrent_00617EEDC3E023C9454F0EEB40422BF5_label_en-US" xlink:label="lab_us-gaap_AccountsReceivableNetCurrent_00617EEDC3E023C9454F0EEB40422BF5" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounts Receivable, Net, Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_00617EEDC3E023C9454F0EEB40422BF5" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AccountsReceivableNetCurrent_00617EEDC3E023C9454F0EEB40422BF5" xlink:to="lab_us-gaap_AccountsReceivableNetCurrent_00617EEDC3E023C9454F0EEB40422BF5" xlink:type="arc" />
    <link:label id="lab_us-gaap_InventoryNet_4CBA27028EED97BE87100EEB40421C4D_terseLabel_en-US" xlink:label="lab_us-gaap_InventoryNet_4CBA27028EED97BE87100EEB40421C4D" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Inventory, net of allowance for obsolescence of $225 and $128, respectively</link:label>
    <link:label id="lab_us-gaap_InventoryNet_4CBA27028EED97BE87100EEB40421C4D_label_en-US" xlink:label="lab_us-gaap_InventoryNet_4CBA27028EED97BE87100EEB40421C4D" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Inventory, Net</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InventoryNet" xlink:label="loc_us-gaap_InventoryNet_4CBA27028EED97BE87100EEB40421C4D" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InventoryNet_4CBA27028EED97BE87100EEB40421C4D" xlink:to="lab_us-gaap_InventoryNet_4CBA27028EED97BE87100EEB40421C4D" xlink:type="arc" />
    <link:label id="lab_us-gaap_PrepaidTaxes_074045512D8323DDEF650EEB40423BAC_terseLabel_en-US" xlink:label="lab_us-gaap_PrepaidTaxes_074045512D8323DDEF650EEB40423BAC" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Prepaid income taxes</link:label>
    <link:label id="lab_us-gaap_PrepaidTaxes_074045512D8323DDEF650EEB40423BAC_label_en-US" xlink:label="lab_us-gaap_PrepaidTaxes_074045512D8323DDEF650EEB40423BAC" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Prepaid Taxes</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_PrepaidTaxes" xlink:label="loc_us-gaap_PrepaidTaxes_074045512D8323DDEF650EEB40423BAC" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PrepaidTaxes_074045512D8323DDEF650EEB40423BAC" xlink:to="lab_us-gaap_PrepaidTaxes_074045512D8323DDEF650EEB40423BAC" xlink:type="arc" />
    <link:label id="lab_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_D923588BA71AC0D850FF0EEB4042F179_terseLabel_en-US" xlink:label="lab_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_D923588BA71AC0D850FF0EEB4042F179" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Prepaid expenses and other</link:label>
    <link:label id="lab_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_D923588BA71AC0D850FF0EEB4042F179_label_en-US" xlink:label="lab_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_D923588BA71AC0D850FF0EEB4042F179" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Prepaid Expense and Other Assets, Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_D923588BA71AC0D850FF0EEB4042F179" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_D923588BA71AC0D850FF0EEB4042F179" xlink:to="lab_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_D923588BA71AC0D850FF0EEB4042F179" xlink:type="arc" />
    <link:label id="lab_us-gaap_AssetsCurrent_7378E7F081845BD037A50EEB4042DC34_totalLabel_en-US" xlink:label="lab_us-gaap_AssetsCurrent_7378E7F081845BD037A50EEB4042DC34" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total current assets</link:label>
    <link:label id="lab_us-gaap_AssetsCurrent_7378E7F081845BD037A50EEB4042DC34_label_en-US" xlink:label="lab_us-gaap_AssetsCurrent_7378E7F081845BD037A50EEB4042DC34" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Assets, Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_7378E7F081845BD037A50EEB4042DC34" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AssetsCurrent_7378E7F081845BD037A50EEB4042DC34" xlink:to="lab_us-gaap_AssetsCurrent_7378E7F081845BD037A50EEB4042DC34" xlink:type="arc" />
    <link:label id="lab_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858_terseLabel_en-US" xlink:label="lab_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Rental equipment, net of accumulated depreciation of $106,179 and $86,533, respectively</link:label>
    <link:label id="lab_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858_label_en-US" xlink:label="lab_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Rental Equipment, Net</link:label>
    <link:label id="lab_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858_documentation_en-US" xlink:label="lab_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Rental Equipment, Net</link:label>
    <link:loc xlink:href="ngs-20141231.xsd#ngs_RentalEquipmentNet" xlink:label="loc_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858" xlink:to="lab_ngs_RentalEquipmentNet_B863E54EBC10F2C4C9BE0EEB40429858" xlink:type="arc" />
    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentOtherNet_7520E42AD1CF430B3EFB0EEB4042CBC6_terseLabel_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentOtherNet_7520E42AD1CF430B3EFB0EEB4042CBC6" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Property and equipment, net of accumulated depreciation of $10,830 and $9,692 respectively</link:label>
    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentOtherNet_7520E42AD1CF430B3EFB0EEB4042CBC6_label_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentOtherNet_7520E42AD1CF430B3EFB0EEB4042CBC6" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment, Other, Net</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_PropertyPlantAndEquipmentOtherNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentOtherNet_7520E42AD1CF430B3EFB0EEB4042CBC6" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentOtherNet_7520E42AD1CF430B3EFB0EEB4042CBC6" xlink:to="lab_us-gaap_PropertyPlantAndEquipmentOtherNet_7520E42AD1CF430B3EFB0EEB4042CBC6" xlink:type="arc" />
    <link:label id="lab_us-gaap_Goodwill_59CD85894B0A1DF188020EEB4042A507_terseLabel_en-US" xlink:label="lab_us-gaap_Goodwill_59CD85894B0A1DF188020EEB4042A507" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Goodwill</link:label>
    <link:label id="lab_us-gaap_Goodwill_59CD85894B0A1DF188020EEB4042A507_label_en-US" xlink:label="lab_us-gaap_Goodwill_59CD85894B0A1DF188020EEB4042A507" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Goodwill</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_59CD85894B0A1DF188020EEB4042A507" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_Goodwill_59CD85894B0A1DF188020EEB4042A507" xlink:to="lab_us-gaap_Goodwill_59CD85894B0A1DF188020EEB4042A507" xlink:type="arc" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseByMajorPropertyClassTable_7D7A3A90C2FF013099E5BD21F2665253" xlink:type="locator" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems" xlink:label="loc_us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems_CDC14FE3A84A6C0A490DBD21F2668D4B" xlink:type="locator" />
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    <link:label id="lab_ngs_OperatingLeasesOfLessorOriginalTerm_9824A832784DAE598B01BD21F266882E_documentation_en-US" xlink:label="lab_ngs_OperatingLeasesOfLessorOriginalTerm_9824A832784DAE598B01BD21F266882E" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Operating Leases of Lessor, Original Term</link:label>
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