Balance Sheet Components (Tables)

Accounts receivable consists of the following:



	June 30, 2017			December 31, 2016
Accounts receivable, gross	$	5,733		$	3,150
Less: allowance for doubtful accounts	(57		)	(32		)
Accounts receivable, net	$	5,676		$	3,118

The following is the change in our allowance for doubtful accounts:



	Six Months Ended
	June 30,
	2017		2016
Balance at beginning of period	$	32	$	60
Additions charged (reductions credited)	25		(21		)
Balance at end of period	$	57	$	39

Inventories consist of the following:

Property and equipment consists of the following:



	June 30, 2017			December 31, 2016
Gross carrying amount	$	25,363		$	24,416
Less: accumulated depreciation and amortization	(20,727		)	(20,623		)
Property and equipment, net	$	4,636		$	3,793

Accrued liabilities and current portion of long-term liabilities consist of the following:



	June 30, 2017		December 31, 2016
Accrued payroll and related liabilities	$	3,468	$	2,169
Accrued commissions and royalties	2,751		2,427
Accrued interest payable	2,303		2,078
Deferred research and development reimbursement	1,311		—
Current portion of accrued liabilities for asset financings	1,013		389
Liability for warranty returns	33		28
Accrued costs related to restructuring	—		60
Other	2,362		709
Accrued liabilities and current portion of long-term liabilities	$	13,241	$	7,860

The following is the change in our liability for warranty returns:



	Six Months Ended
	June 30,
	2017			2016
Liability for warranty returns:
Balance at beginning of period	$	28		$	49
Provision (benefit)	10			(4		)
Charge-offs	(5		)	(18		)
Balance at end of period	$	33		$	27