STOCK-BASED COMPENSATION PLANS

We have granted employees options to purchase shares of our common stock and issued shares of restricted common stock subject to vesting. We measure stock-based compensation cost at the grant date based on the calculated fair value of the option or award. We recognize the expense over the employees' requisite service period, generally the vesting period of the option or award. We estimate the fair value of stock options at the grant date using the Black-Scholes option pricing model. Stock option pricing model input assumptions such as expected term, expected volatility and risk-free interest rate, impact the fair value estimate. Further, the forfeiture rate impacts the amount of aggregate compensation. These assumptions are subjective and generally require significant analysis and judgment to develop.

The following table summarizes the amount of stock-based compensation, net of estimated forfeitures, included in the consolidated statements of operations and comprehensive loss (in thousands):



	Year Ended December 31,
	2018		2017		2016
Costs of customer support	$	165	$	167	$	1,159
Sales, general and administrative	4,513		2,873		3,838
	$	4,678	$	3,040	$	4,997

We have not recognized any tax benefits associated with stock-based compensation due to our tax net operating losses. During the year ended December 31, 2018, an immaterial amount of stock-based compensation was capitalized. During the years ended December 31, 2017 and 2016, we capitalized $0.1 million and $0.2 million, respectively, of stock-based compensation.

During the years ended December 31, 2018 and 2017, there were no options granted under our stock-based compensation plans. The significant weighted average assumptions used for estimating the fair value of the option grants under our stock-based compensation plans during the year ended December 31, 2016, was expected term of 4.7 years; historical volatilities of 45%; risk free interest rates of 1.2%, and no dividend yield. The weighted average estimated fair value per share of our stock options at grant date was $3.13 during the year ended December 31, 2016. The expected term represents the weighted average period of time that the stock options are expected to be outstanding, giving consideration to the vesting schedules and our historical exercise patterns. Because our stock options are not publicly traded, assumed volatility is based on the historical volatility of our stock. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding to the expected term of the options. We have also used historical data to estimate stock option exercises, employee terminations and forfeiture rates.

Under our 2017 Stock Incentive Plan (the "2017 Plan"), we may issue restricted stock and restricted stock units to eligible employees and directors to promote interest of the Company. The compensation committee of our board of directors administers the 2017 Plan. As of December 31, 2018, 1.3 million shares of stock were available for issuance. Conditions, if any, under which stock will be issued under stock grants or cash or stock will be paid under restricted stock units and the conditions under which the interest in any stock that has been issued will become non-forfeitable are determined at the grant date by the compensation committee. All awards under the 2017 Plan are subject to minimum vesting requirements unless otherwise determined by the compensation committee. The minimum vesting period over which stock award shall vest is one year from the date the award is granted. If awards are performance-based, unless otherwise determined by the compensation committee, stock awards to covered employees will be designed to comply with the performance goals. In such case, the level of vesting of the award will depend on the attainment of one or more performance goals. No participant in any calendar year shall be granted stock awards with respect to more than 350,000 shares of stock. Under the 2017 Plan, only full value shares in the form of restricted stock and restricted stock units will be available for grant. Shares of common stock that are delivered by the grantee or withheld by us as payment of the tax withholding obligation in connection with any award will not be returned to the share reserve and will not be available for future awards. Shares subject to awards that have been canceled, forfeited or otherwise not issued under an award and shares subject to awards settled in cash would not count as shares issued under the 2017 Plan.

During the years ended December 31, 2018, 2017 and 2016, the total value of the equity grants received by all non-employee directors was $0.7 million, $1.1 million and $0.4 million, respectively, in the form of restricted stock that vests on the date of our annual meeting of stockholders in the year following grant.

Stock option activity during the year ended December 31, 2018 under all of our stock-based compensation plans was as follows (shares in thousands):



	Shares		Weighted Average Exercise Price
Balance, December 31, 2017	379		$	21.17
Granted	—		—
Exercised	(6	)	8.49
Forfeitures and post-vesting cancellations	(150	)	14.55
Balance, December 31, 2018	223		25.95
Exercisable, December 31, 2018	211		26.74

Fully vested and exercisable stock options and stock options expected to vest as of December 31, 2018 are further summarized as follows (shares in thousands):



	Fully Vested and Exercisable		Expected to Vest
Total shares	211		223
Weighted-average exercise price	$	26.74	$	25.95
Aggregate intrinsic value	$	—	$	—
Weighted-average remaining contractual term (in years)	3.8		4.0

For the year ended December 31, 2018, the total intrinsic value of stock options exercised was less than $0.1 million, and $0.4 million and $0.1 million during the years ended December 31, 2017 and 2016, respectively. None of our stock options or the underlying shares are subject to any right to repurchase by us.

Restricted stock activity during the year ended December 31, 2018 was as follows (shares in thousands):



	Shares		Weighted- Average Grant Date Fair Value
Unvested balance, December 31, 2017	760		$	4.03
Granted	608		$	7.73
Vested	(277	)	$	6.95
Forfeited	(133	)	$	6.61
Unvested balance, December 31, 2018	958		$	5.17

The total fair value of restricted stock vested during the years ended December 31, 2018, 2017 and 2016 was $1.7 million, $2.6 million and $1.5 million, respectively. At December 31, 2018, the total intrinsic value of all unvested restricted stock was $4.0 million.

Total unrecognized compensation costs related to unvested stock-based compensation as of December 31, 2018 is as follows (dollars in thousands):



	Stock Options		Restricted Stock		Total
Unrecognized compensation	$	53	$	3,330	$	3,383
Weighted-average remaining recognition period (in years)	1.03		2.90		2.90