The 2020 Equity Incentive Plan (“2020 Plan”), which permits the granting of non-statutory stock options, restricted stock, restricted stock units, stock appreciation rights, performance units, performance shares and other equity-based awards to employees, directors and consultants, became effective on August 5, 2020. As of December 31, 2020, 2,193,360 shares of common stock were authorized for issuance under the 2020 Plan and 1,032,016 shares remain available for issuance under the 2020 Plan.

The Company’s 2011 Equity Incentive Plan (the “2011 Plan”) permits the granting of incentive stock options, non-statutory stock options, restricted stock, restricted stock units and other stock-based awards to employees, directors, officers and consultants. As of December 31, 2020, 2,764,600 shares of common stock were authorized for issuance under the 2011 Plan and no shares remain available for issuance under the 2011 Plan. No additional awards will be granted under the 2011 Plan. Shares that become available for issuance from the outstanding awards under the 2011 Plan due to forfeiture, or otherwise, will become available for issuance of future awards under the 2020 Plan.

The stock options generally vest over four years and have a ten-year contractual term. The fair value of each employee and non-employee stock option grant is estimated on the date of grant using the Black-Scholes option pricing model. The Company’s common stock became publicly traded in August 2020 and lacks company-specific historical and implied volatility information. Therefore, the Company estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies. Due to the lack of historical exercise history, the expected term of the Company’s stock options has been determined using the “simplified” method for awards. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is zero based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The following assumptions were used to estimate the fair value of stock option for the years ended December 31, 2020 and 2019:

	Year Ended December 31,
	2020		2019
Risk-free interest rate	0.35% - 0.9%		1.6% - 2.1%
Expected dividend yield	—		—
Expected term in years		7.0	6.4 - 10.0
Expected volatility	60% - 80%		80%

The following table summarizes stock option activity during the years ended December 31, 2020 and 2019:

	Stock Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2018		1,587,410		$	8.13		8.0	$	6,012
Options granted		540,157			13.37
Options exercised		(27,806	)		3.87			$	251
Options forfeited		(58,556	)		9.86
Outstanding as of December 31, 2019		2,041,205		$	9.52		7.7	$	10,782
Options granted		1,794,895			16.91
Options exercised		(172,312	)		7.52			$	1,660
Options forfeited		(260,181	)		12.10
Outstanding as of December 31, 2020		3,403,607		$	13.32		8.1	$	52,866
Options vested and exercisable as of December 31, 2020		1,403,764		$	9.55		6.6	$	27,035

The aggregate intrinsic value for options outstanding in the above table represents the product of the number of options outstanding multiplied by the difference between the per share fair value of the Company’s stock on the last day of the fiscal period, which was $28.81, $14.81 and $11.91 as of December 31, 2020, 2019 and 2018, respectively, and the exercise price. The aggregate intrinsic value for options exercised in the above table represents the product of the number of options exercised multiplied by the difference between the per share fair value of the Company’s stock on the date of exercise and the exercise price. The intrinsic value amounts reflected for 2018 and 2019 have been revised from what was previously disclosed. The weighted-average grant date fair value per share for the stock option grants during the years ended December 31, 2020 and 2019 was $11.58 and $9.72, respectively. As of December 31, 2020, the total unrecognized compensation related to unvested stock option awards granted was $28.0 million, which the Company expects to recognize over a weighted-average period of approximately 2.8 years.

Performance-Based Restricted Stock Units (“PSUs”) and Restricted Stock Units (“RSUs”)

In June 2019, the Company granted 567,509 PSUs, with a grant date fair value of $13.37. Vesting of the PSUs was dependent upon the satisfaction of both a service condition and a performance condition, which is an IPO or a change of control. The Company began recording compensation expense related to the PSUs upon the declaration of the Company’s IPO becoming effective on August 5, 2020, as the performance conditions were satisfied. The compensation expense was determined using the original grant date fair value and is being recognized over the remaining service period.

The Company’s PSU and RSU activity for the years ended December 31, 2020 and 2019 was as follows:

	Number of Shares			Weighted Average Grant Price
Unvested as of December 31, 2018		-		$	-
Granted		567,509			13.37
Unvested as of December 31, 2019		567,509		$	13.37
Granted		270,718			19.87
Forfeited		(7,386	)		18.00
Vested		(285,375	)		13.37
Unvested as of December 31, 2020		545,466		$	16.53

The Company’s RSA activity for the years ended December 31, 2020 and 2019 was as follows:

	Number of Shares			Weighted Average Grant Price
Unvested as of December 31, 2018		-		$	-
Granted		11,449			13.37
Vested		(11,449	)		13.37
Unvested as of December 31, 2019		-		$	-
Granted		34,051			16.85
Vested		(34,051	)		16.85
Unvested as of December 31, 2020		-		$	-

The following table summarizes the total stock-based compensation expense for the stock options, PSUs, RSUs and RSAs recorded in the consolidated statements of operations and comprehensive loss for the years ended December 31, 2020 and 2019 (in thousands):

	Year Ended December 31,
	2020		2019
Cost of products sold	$	440	$	209
Research and development		1,002		656
Selling, general and administrative		10,661		2,129
Total stock-based compensation	$	12,103	$	2,994

The 2020 Employee Stock Purchase Plan (“2020 ESPP”), which permits employees to purchase shares of the Company’s common stock, became effective on August 5, 2020 and 387,063 shares of common stock were authorized for sale under the 2020 ESPP. As of December 31, 2020, there were no purchases of shares under the 2020 ESPP as the program does not become effective until February 2021.