3.	Balance Sheet Components

Property and Equipment

Property and equipment consisted of the following (in thousands):

	March 31, 2018			December 31, 2017
Prototype	$	11,938		$	11,929
Machinery and equipment		9,731			7,831
Leasehold improvements		4,565			4,438
Software		1,120			1,142
Furniture and fixtures		588			558
Property and equipment, gross		27,942			25,898
Less: accumulated depreciation and amortization		(14,987	)		(14,334	)
Property and equipment, net	$	12,955		$	11,564

Depreciation and amortization expense related to property and equipment were $653 thousand and $462 thousand during the three months ended March 31, 2018 and 2017, respectively.

Intangible Assets

Intangible assets consisted of the following (in thousands):

	March 31, 2018			December 31, 2017
License cost	$	512		$	512
Patents		104			104
Intangible assets, gross		616			616
Accumulated amortization		(543	)		(538	)
Intangible assets, net	$	73		$	78

Intangible assets amortization expense was $5,000 for each of the three months ended March 31, 2018 and 2017. Amortization of intangible assets was recorded in general and administrative expenses in the condensed consolidated statements of operations.

At March 31, 2018, the estimated future amortization expense of intangible assets was as follows (in thousands):

Year Ending December 31,	Estimated Future Amortization Expense
The remainder of 2018	$	14
2019		19
2020		19
2021		10
2022		3
2023		1
Thereafter		7
Total amortization expense	$	73

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	March 31, 2018		December 31, 2017
Accrued payroll and related benefits	$	5,062	$	3,944
Accrued accounts payable		2,180		2,671
Accrued legal, accounting and governance fees		198		322
Tax payable		401		149
Other		56		121
Total accrued liabilities	$	7,897	$	7,207

Deferred Revenue

Deferred revenue consisted of the following (in thousands):

	March 31, 2018			December 31, 2017
Deferred revenue:
Product	$	6,551		$	18,861
Services		3,234			1,182
Distribution rights		3,228			3,346
Total deferred revenue		13,013			23,389
Less: current portion of deferred revenue		(9,670	)		(20,151	)
Noncurrent portion of deferred revenue	$	3,343		$	3,238