Balance Sheet Components - Property and Equipment Net (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Property and Equipment, Net
Total property and equipment, gross	$ 15,586	$ 14,765
Less: accumulated depreciation	(12,107)	(10,479)
Total property and equipment, net	3,479	4,286
Depreciation and amortization expense	1,700	1,500
Manufacturing equipment
Property and Equipment, Net
Total property and equipment, gross	12,228	11,723
Computer and network equipment
Property and Equipment, Net
Total property and equipment, gross	877	820
Furniture and fixtures
Property and Equipment, Net
Total property and equipment, gross	112	110
Software
Property and Equipment, Net
Total property and equipment, gross	925	680
Leasehold improvements
Property and Equipment, Net
Total property and equipment, gross	$ 1,444	$ 1,432

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount of expense for allocation of cost of tangible and intangible assets over their useful lives directly used in production of good and rendering of service.

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