The Company maintains the 2015 Incentive Plan. The 2015 Incentive Plan was amended and restated in May 2022 to, among other things, increase the number of shares reserved for issuance by 6,935 shares (as amended and restated, the “2015 Plan”). The total number of shares of common stock reserved and available for distribution under the 2015 Plan and the total number of shares of common stock that can be issued pursuant to stock options is 25,235 shares.

The 2015 Plan authorizes the granting of shares of restricted stock, restricted stock units ("RSUs"), stock appreciation rights, cash incentive awards and options to purchase shares of our common stock. The 2015 Plan also designates measures that may be used for performance awards and market-based awards. The Director Plan authorizes the granting of shares of restricted stock to our non-employee directors.

The vesting period for awards under the stock plans is generally determined by the Board of Directors at the date of the grant, and generally the awards vest one third each year, over 3 years. Stock-based compensation expense is included in selling, general and administrative expenses in the consolidated statements of operations.

Included in the above expenses for the years ended December 31, 2022, 2021, 2020 are $4,030, $22,057, and $0 of expense, respectively, pertaining to annual incentive compensation which is paid in Company shares of common stock. Also, included in the above expenses for the years ended December 31, 2022, 2021, and 2020 are $7,959, $683, and $0, respectively, of expense related to the Volumetric earnout arrangement discussed in Note 3. Finally, the above expenses for the years ended December 31, 2022, 2021 and 2020 include $268, $0 and $0, respectively, of expense related to the dp polar earnout arrangement discussed in Note 3.


(in thousands, except per share amounts)	Number of Shares/Units	Weighted Average Grant Date Fair Value
Outstanding at beginning of year — unvested	3,980	$	19.72
Granted	4,422	$	15.23
Canceled	(700)	$	16.90
Vested	(2,687)	$	15.92
Outstanding at end of year — unvested	5,015	$	18.19

Included in the above outstanding balance as of December 31, 2022 are 834 shares of restricted stock that vest under specified market conditions and 1,215 shares of restricted stock that vest under specified Company performance measures. Awards with specified market conditions were awarded to certain employees in 2022, 2021, and 2020.

Included in the above granted and vested activity for the year ended December 31, 2022 are 1,286 shares of stock related to the Company's annual incentive plan that were granted under the 2015 Plan in lieu of cash and immediately vested in the first quarter of 2022.

On December 1, 2021, we issued Performance Share Units (PSUs) to employees of Volumetric as part of the acquisition agreement. Vesting of these shares is based on four non-financial milestones that involve various medical achievements. These awards were divided into four tranches, one tranche per milestone, and compensation expense is recognized only when a milestone is probable of achievement. During the year ended December 31, 2022, an additional 213 PSUs with corresponding milestones were issued to employees. As of December 31, 2022 and 2021, one of the four milestones was deemed probable of achievement and, accordingly, the company recognized expense related to these awards of $1,031 and $81 for the years ended December 31, 2022 and 2021, respectively.

At December 31, 2022, there was $46,601 of unrecognized stock-based compensation expense related to all unvested restricted stock and RSUs, which we expect to recognize over a weighted-average period of 1.9 years.

During the year ended December 31, 2016, we awarded certain employees market condition stock options under the 2015 Plan that vest under specified market conditions. Each employee was generally awarded two equal tranches of market condition stock options that immediately vest when our common stock trades at either $30 or $40 per share for ninety consecutive calendar days.

We recognize compensation expense related to stock options on a straight-line basis over the derived term of the awards. The fair value of stock options with market conditions is estimated using a binomial lattice Monte Carlo simulation model. Expense for awards with a market condition is not reversed if the market condition is not met.


	Year Ended December 31, 2022
(in thousands, except per share amounts)	Number of Shares	Weighted Average Exercise		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Stock option activity:
Outstanding at beginning of year	420	$	13.26	4.7	$	3,479
Granted	—	—		—	—
Exercised	—	—		—	—
Forfeited and expired	—	—		—	—
Outstanding at end of year	420	$	13.26	3.7	$	—

As of December 31, 2022 and 2021, none of the 420 outstanding stock options were exercisable, and there was no unrecognized stock-based compensation expense related to stock options.