Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2023

Stock-Based Compensation

Summary of share-based compensation expense for all stock awards

Stock-based compensation expense was recorded in the following categories on the Consolidated Statements of Operations (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Cost of product revenue	$	224	$	199	$	611	$	424
Cost of service and other revenue		259		159		867		530
Research and development		449		320		1,224		1,200
Selling, general, and administrative		3,411		2,088		9,736		9,625
Total stock-based compensation	$	4,343	$	2,766	$	12,438	$	11,779

Summary of stock option activity

Stock Options

Stock option activity for the nine months ended September 30, 2023 is presented below (in thousands, except per share and contractual life amounts):

				Weighted-average
		Weighted-average		remaining contractual	Aggregate
	Number of shares	exercise price per share		life (in years)	intrinsic value
Outstanding at December 31, 2022	2,188	$	20.69	8.1	$	4,273
Granted	1,102		15.74
Exercised	(132)		12.37
Cancelled	(418)		18.51
Outstanding at September 30, 2023	2,740	$	19.43	8.1	$	26,822
Exercisable at September 30, 2023	967	$	23.71	6.3	$	7,260
Vested and expected to vest at September 30, 2023	2,740	$	19.43	8.1	$	26,822

Summary of restricted stock units activity

Restricted Stock Units

Restricted stock unit (“RSU”) activity for the nine months ended September 30, 2023 is presented below (in thousands, except per share and contractual life amounts):

		Weighted-average		Weighted-average
		grant date fair		remaining contractual	Aggregate
	Number of shares	value per share		life (in years)	intrinsic value
Unvested RSUs at December 31, 2022	1,188	$	21.18	9.6	$	16,455
Granted	812		15.49
Vested	(306)		24.52
Cancelled	(258)		17.59
Unvested RSUs at September 30, 2023	1,436	$	17.90	9.1	$	38,976
Expected to convert at September 30, 2023	1,436	$	17.90	9.1	$	38,976

Summary of fair value of the Company's stock options granted and purchase rights to the ESPP

The fair value of the Company’s stock options granted and purchase rights to the ESPP were estimated using the Black-Scholes valuation model with the following assumptions:

	Three Months Ended September 30,				Nine Months Ended September 30,
		2023		2022		2023		2022
Stock Options:
Risk-free interest rate		4.0% − 4.4%		2.7% − 3.9%		3.5% − 4.4%		1.4% − 3.9%
Expected dividend yield		None		None		None		None
Expected term (in years)		5.1		5.5 − 5.7		5.0 − 5.1		5.5 − 5.8
Expected volatility		82.6% − 83.1%		62.6% − 69.8%		71.1% − 83.1%		55.0% − 69.8%
Weighted-average grant date fair value	$	16.82	$	5.80	$	10.25	$	10.28
Employee Stock Purchase Plan:
Risk-free interest rate		5.5%		3.3% - 3.9%		5.2% - 5.5%		0.7% - 3.9%
Expected dividend yield		None		None		None		None
Expected term (in years)		0.5		0.5		0.5		0.5
Expected volatility		74.7% − 78.5%		115.3% − 117.3%		72.8% − 82.5%		51.9% − 117.3%
Weighted-average grant date fair value	$	4.39	$	3.02	$	2.63	$	3.85