Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Total revenue	$ 10,108	$ 10,026
Cost of sales	4,757	5,241
Gross profit	5,351	4,785
Operating expenses:
Research and development	3,030	3,998
General and administrative	2,800	3,595
Sales and marketing	1,103	1,364
Total operating expenses	6,933	8,957
Loss from operations	(1,582)	(4,172)
Interest expense	(172)	(211)
Other income, net	22	127
Net loss and comprehensive loss	$ (1,732)	$ (4,256)
Net loss per common share, basic and diluted	$ (0.10)	$ (0.25)
Weighted-average shares used to compute net loss per common share, basic and diluted	18,055,693	17,097,999
Operating expenses include stock-based compensation as follows:
Total stock-based compensation	$ 805	$ 704
Research and development
Operating expenses include stock-based compensation as follows:
Total stock-based compensation	162	147
General and administrative
Operating expenses include stock-based compensation as follows:
Total stock-based compensation	585	509
Sales and marketing
Operating expenses include stock-based compensation as follows:
Total stock-based compensation	58	48
Product sales
Total revenue	9,635	9,023
Product sales
Total revenue	9,635	9,023
Licensing, royalty and other revenue
Total revenue	$ 473	$ 1,003