We grant RSUs, and prior to January 2020 we granted RSAs, to participants in our equity plans. Performance-based RSUs granted in the nine months ended September 28, 2024 included certain grants that vest based on our total shareholder return ranking relative to the Nasdaq US Benchmark Auto Parts Index over a three-year performance period (market condition), and other grants that vest based upon achievement of return on invested capital targets over a three-year performance period (performance condition).

Compensation cost related to RSA and RSU grants was $3.4 million and $2.4 million for the three months ended September 28, 2024 and September 30, 2023, respectively, and $9.1 million and $6.7 million for the nine months ended September 28, 2024 and September 30, 2023, respectively, and was included in selling, general and administrative expenses in the Condensed Consolidated Statements of Operations.

The following table summarizes our RSA and RSU activity for the nine months ended September 28, 2024:


	Shares	Weighted Average Fair Value
Balance at December 31, 2023	257,554	$	97.33
Granted	187,645	$	98.95
Vested	(72,701)	$	89.90
Canceled	(28,792)	$	112.06
Balance at September 28, 2024	343,706	$	98.56

For the nine months ended September 28, 2024, we granted 32,109 performance-based RSUs containing a market condition with a grant date fair value of $138.58 per share. For the nine months ended September 30, 2023, we granted 29,399 performance-based RSUs containing a market condition with a grant date fair value of $113.15 per share.

As of September 28, 2024, there was $21.7 million of unrecognized compensation cost related to unvested RSA and RSU grants that is expected to be recognized over a weighted average period of 2.1 years.

From time to time, we grant stock options to participants in our equity plans. Compensation cost related to stock option grants was $0.3 million and $0.5 million for the three months ended September 28, 2024 and September 30, 2023, respectively, and $1.1 million and $1.5 million for the nine months ended September 28, 2024 and September 30, 2023, respectively, and was included as selling, general and administrative expenses in the Condensed Consolidated Statements of Operations.

The following table summarizes our stock option activity for the nine months ended September 28, 2024:


	Shares	Weighted Average Price		Weighted Average Remaining Term (years)	Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2023	311,217	$	86.52

Canceled	(10,936)	$	95.80
Exercised	(25,580)	$	72.88
Balance at September 28, 2024	274,701	$	87.42	4.7	$	7,187
Exercisable at September 28, 2024	174,775	$	83.34	4.1	$	5,284

As of September 28, 2024, there was $2.5 million of unrecognized compensation cost related to unvested stock options that is expected to be recognized over a weighted average period of 2.1 years.

During the nine months ended September 28, 2024, we issued 13,555 shares under the ESPP. During the nine months ended September 30, 2023, we issued 14,975 shares under the ESPP.