Selected Balance Sheet Components

Inventory as of June 30, 2016 and December 31, 2015:



(In thousands)	June 30, 2016		December 31, 2015
Raw materials	$	2,089	$	1,228
Work-in-process	276		131
Finished goods	28		20
Inventory	$	2,393	$	1,379

Property and equipment, net as of June 30, 2016 and December 31, 2015:



(In thousands)	June 30, 2016			December 31, 2015
Machinery and equipment	$	3,200		$	3,280
Furniture, fixtures and office equipment	931			931
Computer equipment and software	2,662			2,662
Leasehold improvements	3,291			2,393
Construction in process	593			421
Total property and equipment, gross	10,677			9,687
Less: Accumulated depreciation	(6,326		)	(5,638		)
	$	4,351		$	4,049

The leasehold improvements include $0.9 million of tenant reimbursed improvements to our cleanrooms to replace a rooftop air handler unit. The leasehold improvement is accounted for as a lease incentive under lease accounting guidance.

Depreciation expense for the three and six months ended June 30, 2016 was $0.4 million and $0.8 million, respectively, compared to $0.2 million and $0.5 million, respectively, for the same periods in 2015.

Intangible assets, net as of June 30, 2016 and December 31, 2015:



(In thousands)	June 30, 2016			December 31, 2015
Commercial rights	$	3,360		$	3,360
Less: accumulated amortization	$	(582	)	$	(443	)
	$	2,778		$	2,917

The calculated value of the commercial rights intangible assets are amortized using the straight line method over an estimated useful life of 12 years. Amortization expense for both the three and six months ended June 30, 2016 and 2015 was $0.1 million and $0.2 million, respectively.

Estimated future amortization expense is as follows:



Calendar Years Ending December 31, (In thousands)
2016	$	141
2017	280
2018	280
2019	280
2020	280
Thereafter	1,517
Total	$	2,778

Accrued expenses as of June 30, 2016 and December 31, 2015:



(In thousands)	June 30, 2016		December 31, 2015
Bonus related compensation	$	1,325	$	1,956
Employee related accruals	1,485		1,341
Accrued expenses	82		306
	$	2,892	$	3,603