3.	Balance Sheet Components

Property and Equipment

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

	June 30, 2017			December 31, 2016
Prototype	$	11,929		$	6,405
Machinery and equipment		6,739			6,057
Leasehold improvements		4,371			4,371
Software		1,050			1,028
Furniture and fixtures		450			368
Construction in progress		—			5,498
Property and equipment, gross		24,539			23,727
Less: accumulated depreciation and amortization		(13,151	)		(12,167	)
Property and equipment, net	$	11,388		$	11,560

Depreciation and amortization expense related to property and equipment were $532 thousand and $438 thousand during the three months ended June 30, 2017 and 2016, respectively, and $994 thousand and $764 thousand during the six months ended June 30, 2017 and 2016, respectively.

Intangible Assets

Intangible assets consisted of the following (in thousands):

	June 30, 2017			December 31, 2016
License cost	$	512		$	512
Patents		104			104
Intangible assets, gross		616			616
Accumulated amortization		(529	)		(519	)
Intangible assets, net	$	87		$	97

Intangible assets amortization expense were $5 thousand and $46 thousand during the three months ended June 30, 2017 and 2016, respectively, and $10 thousand and $92 thousand during the six months ended June 30, 2017 and 2016, respectively. Amortization of intangible assets was recorded in general and administrative expenses in the condensed consolidated statements of operations.

At June 30, 2017, the estimated future amortization expense of intangible assets was as follows (in thousands):

Year Ending December 31,	Estimated Future Amortization Expense
The remainder of 2017	$	10
2018		19
2019		19
2020		19
2021		10
2022		3
Thereafter		7
Total amortization expense	$	87

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	June 30, 2017		December 31, 2016
Accrued payroll and related benefits	$	3,387	$	4,274
Accrued accounts payable		2,860		1,202
Accrued legal, accounting and governance fees		483		509
Sales tax payable		53		13
Other		703		336
Total accrued liabilities	$	7,486	$	6,334

Deferred Revenue

Deferred revenue consisted of the following (in thousands):

	June 30, 2017			December 31, 2016
Deferred revenue:
Product	$	11,950		$	5,050
Services		1,834			1,561
Distribution rights		3,585			3,822
Total deferred revenue		17,369			10,433
Less: current portion of deferred revenue		(13,787	)		(6,515	)
Noncurrent portion of deferred revenue	$	3,582		$	3,918