We maintain two stockholder approved plans for the issuance of stock-based compensation awards to our employees and Board of Director members: (i) the 2019 Equity Incentive Plan, as amended (the “Equity Incentive Plan”), and (ii) the 1998 Stock Option Plan, as amended (the “Stock Option Plan”).

(1) Represents compensation expense associated with awards that may be settled in cash at the option of the grantee including a nominal amount (less than $1 thousand) during the 2025 period and none during the 2024 period.

The Stock Option Plan provides for the granting of incentive and non-qualified stock options to our employees for up to 1,000,000 shares of common stock. After consideration of the activity described in the table below, a total of 370,002 shares remained available for grant under the Stock Option Plan as of March 31, 2025. The last date that grants can be made under the Stock Option Plan is February 28, 2026. A summary of all option activity during the three months ended March 31, 2025 is presented below:


	Number of Shares Underlying Stock Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2024	113,751	$	20.44	5.84	$	747
Granted	40,250	$	22.19		$	—
Exercised	—	$	—		$	—
Canceled/Forfeited	(2,833)	$	21.57		$	16
Expired	—	$	—		$	—
Outstanding, March 31, 2025	151,168	$	20.89	6.69	$	344
Exercisable, March 31, 2025	64,921	$	19.98	3.08	$	261


Range of Exercise Prices:	Options Outstanding				Options Exercisable
	Shares	Weighted Average Remaining Contractual Life (years)	Weighted Average Exercise Price		Shares	Weighted Average Exercise Price
$0.01-$18.00	29,501	6.99	$	10.72	22,835	$	10.68

$18.01-$26.00	5,000	9.38	$	19.50	1,169	$	19.65
$26.01-$30.00	116,667	6.49	$	23.51	40,917	$	25.18

	151,168	6.69	$	20.89	64,921	$	19.98


	Shares	Weighted Average Grant Date Fair Value Per Share
Unvested, December 31, 2024	48,998	$	11.35
Granted	40,250	$	12.06
Vested	(501)	$	10.45

Canceled/Forfeited	(2,500)	$	12.46
Unvested, March 31, 2025	86,247	$	11.65

As of March 31, 2025, there was a total of approximately $0.6 million of unrecognized compensation cost related to unvested options which is expected to be recognized over the next 2.54 years.

The Equity Incentive Plan provides for up to 1,150,000 shares of common stock for issuance in the form of awards for: (i) stock options, (ii) stock appreciation rights, (iii) restricted awards in the form of restricted stock and restricted stock units (“RSUs”), (iv) performance share awards, including performance share unit (“PSUs”) and (v) other equity-based awards. After consideration of the activity described in detail below, a total of 166,975 shares remained available for grant under the Equity Incentive Plan as of March 31, 2025.

The following table summarizes all restricted stock and RSU activity during the three months ended March 31, 2025 is presented below:


	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2024	131,183	$	16.39	5.15	$	3,516
Granted	55,859	$	22.19		$	1,240
Exercised	(22,891)	$	15.46		$	580
Canceled/Forfeited	—	$	—		$	—
Outstanding, March 31, 2025	164,151	$	18.50	4.81	$	3,606

As of March 31, 2025, there was a total of approximately $2.1 million of unrecognized compensation cost related to unvested restricted stock and RSUs which is expected to be recognized over the next 2.5 years.

The 2024 grant of RSUs to the independent Board members that can be settled in cash represent liability-classified awards. Compensation expense associated with these awards is based upon the fair value of NGS common stock at each reporting period relative to that portion of the service period that has passed. Accordingly, the compensation expense is variable in nature.


	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2024	15,069	$	19.51	0.50	$	294
Granted	—				$	—
Vested	—				$	—
Canceled/Forfeited	(2,810)	$	19.57		$	55
Outstanding, March 31, 2025	12,259	$	19.50	0.30	$	239

The potential payout for the PSU awards is based upon performance for a three-year period ending December 31, 2026 for the 2024 grants and December 31, 2027 for the 2025 grants measured against relative total shareholder return (“TSR”) compared to a peer group of companies as established by the Compensation Committee. The PSU award payout ranges from zero (if the Company ranks below the 31.25 percentile) and up to 200% (if the Company ranks first) based upon our relative TSR performance ranking (subject to certain caps based on absolute TSR as defined in the PSU agreements).

With respect to vesting, the PSUs have both a service condition and a market condition. Due to the presence of the TSR measurement for the common equity of the peer companies, including NGS common stock, which is deemed a “market condition,” the grant-date fair values of the PSUs have been determined using a binomial pricing model, or a Monte Carlo simulation model.

The following table summarizes the weighted average grant date fair values of PSUs granted and the assumptions used in the Monte Carlo simulation model for the determination of the grant date fair values of our PSUs granted during the three months ended March 31, 2025:


Weighted-average grant date fair value of PSUs granted	$	28.05
Risk free rate	3.93		%
Expected volatility	43.9		%
Expected dividend yield	—		%


	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2024	56,764	$	22.47	2.22	$	—
Granted	39,434	$	28.05		$	—
Vested	—				$	—
Canceled/Forfeited	—				$	—
Outstanding, March 31, 2025	96,198	$	24.76	2.38	$	—

As of March 31, 2024, there was a total of approximately $2.0 million of unrecognized compensation cost related to the unvested portion of the PSUs which is expected to be recognized over the next 2.38 years.