Warrants, stock-based compensation, stock options, restricted stock and restricted stock units (Tables)

9 Months Ended

Sep. 30, 2019

Warrants, stock-based compensation, stock options, restricted stock and restricted stock units

Summary of share-based compensation expense for all stock awards

Stock‑based compensation expense for all stock awards consists of the following (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Cost of product revenue	$	31	$	20	$	75	$	49
Cost of service and other revenue		58		38		175		121
Research and development		175		152		523		361
Selling, general, and administrative		1,564		1,657		3,940		2,862
Total	$	1,828	$	1,867	$	4,713	$	3,393

Summary of stock option activity

		Weighted-average		Remainingcontractual	Aggregateintrinsicvalue
	Options	exerciseprice		life(in years)	(in thousands)
Outstanding at December 31, 2018	2,476,911	$	9.65	7.73	$	22,108
Granted	818,918	$	24.25
Exercised	(322,250)	$	6.74
Cancelled	(311,245)	$	13.45
Outstanding at September 30, 2019	2,662,334	$	14.04	7.72	$	23,476
Vested and expected to vest at September 30, 2019	2,662,334	$	14.04	7.72	$	23,476
Exercisable at September 30, 2019	1,234,533	$	7.91	6.40	$	17,394

Summary of restricted stock units activity

		Weighted-average
		grant date
		fair value
	Shares	per share
Unvested RSUs as of December 31, 2018	321,662	$	15.84
Granted	227,653	$	24.21
Vested	(83,996)	$	16.65
Cancelled	(42,983)	$	18.17
Unvested RSUs as of September 30, 2019	422,336	$	19.90