As of September 30, 2023, the 2005 Incentive Plan, as amended, has a total reserve of 32,168,895 shares of which 4,754,771 shares are available for issuance.

The stock-based compensation related to our stock-based awards and employee stock purchase plan for the three and nine months ended September 30, 2023 and 2022 is as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Cost of net revenues	$	1,974	$	1,651	$	5,682	$	4,779
Selling, general and administrative	29,739		25,293		87,432		76,509

Research and development	7,889		5,974		22,083		17,391
Total stock-based compensation	$	39,602	$	32,918	$	115,197	$	98,679

The fair value of RSUs is based on our closing stock price on the date of grant. RSUs granted generally vest over a period of four years. A summary for the nine months ended September 30, 2023 is as follows:


	Number of Shares Underlying RSUs (in thousands)	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Unvested as of December 31, 2022	489	$	427.24
Granted	508	316.52
Vested and released	(196)	378.93
Forfeited	(37)	388.56
Unvested as of September 30, 2023	764	$	367.93	1.6	$	233,165

As of September 30, 2023, we expect to recognize $202.1 million of total unamortized compensation costs, net of estimated forfeitures, related to RSUs over a weighted average period of 2.8 years.

We grant MSUs to members of senior management. Each MSU represents the right to one share of our common stock. The actual number of MSUs which will be eligible to vest will be based on the performance of Align’s stock price relative to the performance of a stock market index over the vesting period. MSUs vest over a period of three years and the maximum number eligible to vest in the future is 250% of the MSUs initially granted.

The following table summarizes the MSU performance activity for the nine months ended September 30, 2023:


	Number of Shares Underlying MSUs (in thousands)	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Unvested as of December 31, 2022	144	$	725.73
Granted	82	629.53
Vested and released 1	(25)	392.67
Forfeited	(43)	423.87
Unvested as of September 30, 2023	158	$	811.06	1.7	$	48,135

1 Includes MSUs vested during the period below 100% of the original grant as actual shares released is based on Align’s stock performance over the vesting period.

As of September 30, 2023, we expect to recognize $56.8 million of total unamortized compensation costs, net of estimated forfeitures, related to MSUs over a weighted average period of 1.7 years.

During the nine months ended September 30, 2023, we did not grant any PSUs to any employees. As of September 30, 2023, we expect to recognize $0.5 million of total unamortized compensation costs, net of estimated forfeitures, related to PSUs over a weighted average term of 1.3 years. Total PSUs granted were 4,728 and the weighted average grant date fair value for the PSUs was $201.63.

As of September 30, 2023, we have 1,995,520 shares available for future issuance under our Amended and Restated 2010 Employee Stock Purchase Plan (the “2010 Purchase Plan”).

The fair value of the option component of the 2010 Purchase Plan shares was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions:


	Nine Months Ended September 30,
		2023			2022
Expected term (in years)		1.2			1.5
Expected volatility		56.2		%	50.2		%
Risk-free interest rate		4.9		%	1.8		%
Expected dividends		—			—
Weighted average fair value at grant date		$	133.53		$	159.44

As of September 30, 2023, we expect to recognize $11.6 million of total unamortized compensation costs related to future employee stock purchases over a weighted average period of 0.7 years.