The Company has a stock-based compensation plan to attract, motivate, retain and reward employees, directors and consultants by providing its Board or a committee of the Board the discretion to award equity incentives to these persons. The Company’s stock-based compensation plan consists of the 2011 Incentive Compensation Plan (the “2011 Plan”), as amended.

On June 6, 2011, the Company’s stockholders approved the 2011 Plan, which is administered by the Compensation Committee of the Board. The 2011 Plan provides that stock options, stock units, restricted shares, and stock appreciation rights may be granted to executive officers, directors, consultants, and other key employees. The Company reserved 400,000 shares of common stock under the 2011 Plan, plus 459,956 shares of common stock that remained available for delivery under the 2007 Plan and the 2010 Plan as of June 6, 2011. In aggregate, as of June 6, 2011, 859,956 shares were available for future grant under the 2011 Plan, including shares rolled over from 2007 Plan and 2010 Plan. Subsequent to June 6, 2011 through December 31, 2019, the number of shares of common stock authorized for issuance under the 2011 Plan has been increased by 3,500,000 shares.

A summary of activity for the Company’s stock options for the year ended December 31, 2019 follows:

	Number Outstanding			Average Exercise Price per Share		Weighted Average Remaining Contractual Term (Years)		Average Intrinsic Value
Balance at December 31, 2018		621,602		$	5.87	6.32		$	—
Granted		—			—				—
Cancelled or Expired		(57,000	)		8.52				—
Exercised		(2,500	)		5.20				—
Balance at December 31, 2019		562,102		$	5.60		5.86	$	572,869
Vested or expected to vest at December 31, 2019		562,102		$	5.60		5.86	$	572,869
Exercisable at December 31, 2019		562,102		$	5.60		5.86	$	572,869

The following table summarizes information about stock options outstanding as of December 31, 2019:

	Options Outstanding						Options Exercisable
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (Years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$4.36 - $7.20		465,310		6.30	$	4.45		465,310	$	4.45
$7.50 - $11.30		75,198		4.15		9.89		75,198		9.89
$12.00 - $19.70		17,244		2.50		13.60		17,244		13.60
$21.70 - $24.20		4,350		1.67		23.27		4,350		23.27
$4.36 - $24.20		562,102						562,102

At December 31, 2019, there was no of unrecognized stock-based compensation expense related to stock options.

The following is a summary of restricted stock unit (“RSU”) activity for the year ended December 31, 2019:

	Number Outstanding			Weighted Average Fair Value
Balance at December 31, 2018		1,367,630		$	3.81
Granted		577,682			5.03
Vested		(659,170	)		3.62
Forfeited		(138,032	)		4.59
Balance at December 31, 2019		1,148,110			4.43
Shares vested but not released		202,940			5.27

The fair value of the Company’s RSUs is calculated based upon the fair market value of the Company’s common stock at the date of grant. As of December 31, 2019, there was $4.2 million of unrecognized compensation cost related to unvested RSUs granted, which is expected to be recognized over a weighted average period of 2.6 years.

The following table summarizes stock-based compensation expense related to stock options and RSUs included in the consolidated statements of operations for the years ended December 31, 2019 and 2018 (in thousands):

	Year Ended December 31,
	2019		2018
Cost of revenue	$	128	$	89
Research and development		651		488
Selling and marketing		595		689
General and administrative		1,276		1,380
Total	$	2,650	$	2,646

During the years ended December 31, 2019 and 2018, the Company repurchased 175,878 and 141,670 shares, respectively of common stock surrendered to the Company to satisfy tax withholding obligations in connection with the vesting of RSUs issued to employees.