On May 28, 2020, the Company adopted the 2020 Incentive Award Plan (“the 2020 Plan”), which authorized the issuance of (i) up to 3,019,108 shares of the Company’s common stock, (ii) up to 4% of an annual increase on the first day of each year beginning on January 1, 2022 and ending on January 1, 2030, and (iii) any shares of the Company’s common stock subject to awards under the 2014 Plan which are forfeited or lapse unexercised and which following the effective date are not issued under the 2014 Plan. Awards may be issued in the form of restricted stock units, restricted stock, stock appreciation rights, and stock options. As of December 31, 2020, there were 3,185,964 shares available for future issuance under the 2020 Plan.

The following table summarizes stock option activity for the year ended December 31, 2020:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life
Outstanding as of December 31, 2019		6,340,000		$	3.92		8.22
Granted		420,500			10.46
Exercised		(598,406	)		3.91
Forfeited / cancelled		(544,526	)		4.48
Outstanding as of December 31, 2020		5,617,568		$	4.35		7.33
Vested and exercisable as of December 31, 2019		2,684,160		$	3.58		7.41
Vested and exercisable as of December 31, 2020		3,449,606		$	3.83		6.74

The Company recognized $2.2 million, $2.6 million, and $1.0 million of stock-based compensation expense related to stock options for the years ended December 31, 2020, 2019, and 2018, respectively. As of December 31, 2020 and 2019, the Company had $3.5 million and $5.2 million, respectively, of unrecognized stock-based compensation expense that is expected to be recognized over a weighted-average period of 2.2 years and 2.6 years, respectively.

The grant date fair value of stock options granted during the year ended December 31, 2020 was estimated at the time of grant using the Black-Scholes option-pricing model and utilized the following weighted average assumptions:

	Year Ended December 31, 2020
Fair value of common stock (per share)	$	10.46
Expected term (in years)	5.9 — 6.3
Risk-free interest rate	1.7%
Expected volatility	36.3% — 36.6%
Dividend yield	—%

The weighted average fair value of stock options granted during the year ended December 31, 2020 was estimated to be $3.97 per share. The aggregate intrinsic value of options exercised during the year ended December 31, 2020 was $22.4 million, and the aggregate intrinsic value of options outstanding and options exercisable as of December 31, 2020 was $205.7 million and $128.1 million, respectively.

The following table summarizes activity for restricted stock units (“RSUs”) for the year ended December 31, 2020:

	Shares			Weighted Average Grant Date Fair Value per Share
Unvested and outstanding as of December 31, 2019		408,000		$	4.01
Granted		2,073,006			12.06
Vested		(237,334	)		3.86
Forfeited / cancelled		(8,230	)		11.86
Unvested and outstanding as of December 31, 2020		2,235,442		$	11.46

The Company recognized $10.9 million, $0.1 million, and $0.1 million of stock-based compensation expense related to RSUs for the years ended December 31, 2020, 2019, and 2018, respectively. As of December 31, 2020 and 2019, the Company had $15.4 million and $1.3 million, respectively, of unrecognized stock-based compensation expense that is expected to be recognized over a weighted-average period of 1.8 years and 2.4 years, respectively.

As a result of completing its IPO in June 2020, the Company commenced the recognition of compensation expense for 510,278 RSUs that vest upon the occurrence of a liquidity event, which includes an IPO, and continuous service that generally ranges from 12 to 48 months.

In February 2020, the Company granted 367,782 RSUs to its chief executive officer that vest upon the achievement of performance-based conditions, which includes Revenue and EBITDA targets for fiscal year 2022, and the achievement of a liquidity event, which includes a change of control or an IPO. As a result of completing its IPO in June 2020, and the probability of achieving the performance-based conditions, the Company commenced recognition of compensation expense.

Certain of the Company’s RSU grants are subject to acceleration upon a change of control and termination within 12 months, and upon death, disability, retirement and certain “good leaver” circumstances.

During the years ended December 31, 2014 and 2015, the Company granted awards of 4,751,874 shares of restricted common stock (the “RSAs”).

The following table summarizes the activity related to the Company’s RSAs for the year ended December 31, 2020:

For the years ended December 31, 2020, 2019, and 2018, the expense related to the RSAs was $0.2 million, $0.0 million and $0.1 million, respectively. As of December 31, 2020, there was no remaining unrecognized stock-based compensation expense related to the RSAs.