12. Stock-Based Compensation

The Company recognized total stock-based compensation expense during the three and six months ended June 30, 2019 and 2018 as follows:


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019		2018
Service based awards:
Restricted stock awards	$	-	$	1,012,171	$	-	$	1,271,902
Restricted stock units		427,472		-		771,823		-
Stock option awards		547,139		353,161		1,199,163		539,433
		974,611		1,365,332		1,970,986		1,811,335
Performance based awards:
Restricted stock units		402,814		-		801,202		-
Stock option awards		123,901		-		246,440		-
		526,715		-		1,047,642		-
Total	$	1,501,326	$	1,365,332	$	3,018,628	$	1,811,335

Restricted Stock

A summary of the Company’s restricted stock awards during the six months ended June 30, 2019 is as follows:


			Weighted Average
			Grant-Date
	Number of Shares		Fair Value
Unvested at December 31, 2018	146,800	$	5.70
Unvested at June 30, 2019	146,800	$	5.70

A summary of the Company’s restricted stock awards during the six months ended June 30, 2018 is as follows:


			Weighted Average
			Grant-Date
	Number of Shares		Fair Value
Unvested at December 31, 2017	480,000	$	7.27
Unvested at June 30, 2018	480,000	$	7.27

The fair value of restricted stock awards are measured based on their fair value on the date of grant and amortized over the vesting period of 20 months. As of June 30, 2019 unvested restricted stock awards of 146,800 were related to performance based awards.

Service Based Restricted Stock Units

A summary of the Company’s service based restricted stock units during the six months ended June 30, 2019 is as follows:


			Weighted Average
			Grant-Date
	Number of Shares		Fair Value
Unvested at December 31, 2018	472,959	$	4.32
Granted	199,938		4.45
Forfeited	(3,650)		4.81
Unvested at June 30, 2019	669,247	$	4.36

The fair value of service based restricted stock units are measured based on their fair value on the date of grant and amortized over the vesting period. The vesting periods range from 1-3 years. Stock-based compensation expense of $0.4 million and $0.8 million was recognized during the three and six months ended June 30, 2019. No stock-based compensation was recognized during the three and six months ended June 30, 2018, since there were no service based restricted stock units outstanding during that period. As of June 30, 2019, the unrecognized stock-based compensation expense was $1.8 million.

Performance Based Restricted Stock Units

A summary of the Company’s performance based restricted stock units during the six months ended June 30, 2019 is as follows:


			Weighted Average
			Grant-Date
	Number of Shares		Fair Value
Unvested at December 31, 2018	988,958	$	4.48
Unvested at June 30, 2019	988,958	$	4.48

Stock-based compensation expense recognized for performance based restricted stock units was $0.4 million and $0.8 million during the three and six months ended June 30, 2019. No stock-based compensation was recognized during the three and six months ended June 30, 2018, since there were no performance based restricted stock units outstanding during that period. As of June 30, 2019, the unrecognized stock-based compensation expense related to performance based restricted stock units was $1.9 million. In addition, see subsequent events note 17 for potential risk relating to vesting of certain RSU’s granted previously.

Service Based Stock Options

The fair value of the service based stock options granted for the six months ended June 30, 2019 were based on the following assumptions:


	June 30,
	2019
Exercise price	$2.96 - $6.21
Expected stock price volatility	67.5% - 70.3%
Risk-free interest rate	1.9% - 2.6%
Term (years)	5.5 -6.5

A summary of the Company’s service based stock option activity for the six months ended June 30, 2019 is as follows:


				Weighted
			Weighted	Average
	Shares		Average	Remaining		Aggregate
	Underlying		Exercise	Contractual		Intrinsic
	Options		Price	Term		Value
Outstanding at December 31, 2018	7,856,480	$	7.50	5.2	$	-
Granted	523,105	$	4.33	9.7		-
Exercised	(30,000)	$	4.93	-		-
Forfeited	(550,549)		6.67	-		-
Outstanding at June 30, 2019	7,799,036	$	7.36	5.4	$	2,500

Exercisable at June 30, 2019	6,183,193	$	8.16	4.3	$	-

A summary of the Company’s service based stock option activity for the six months ended June 30, 2018 is as follows:


				Weighted
			Weighted	Average
	Shares		Average	Remaining		Aggregate
	Underlying		Exercise	Contractual		Intrinsic
	Options		Price	Term		Value
Outstanding at December 31, 2017	6,906,001	$	7.92	5.0	$	976,335
Forfeited	(100,000)	$	6.93	-
Outstanding at June 30, 2018	6,806,001	$	7.93	4.6	$	629,680

Exercisable at June 30, 2018	6,578,161	$	7.93	4.5	$	629,680

The aggregate intrinsic value in the table above is calculated as the difference between the closing price of our common stock and the exercise price of the stock options that had strike prices below the closing price.

During the six months ended June 30, 2019, the Company granted to certain employee’s stock options to purchase up to 523,105 shares of common stock. During the six months ended June 30, 2019, forfeitures were 550,549. Forfeitures are recorded in the period of occurrence; compensation expense is adjusted accordingly.

Stock-based compensation expense recognized for service based stock options was $0.5 million and $1.2 million for the three and six months ended June 30, 2019 and $0.3 million and $0.5 million for the three and six months ended June 30, 2018. As of June 30, 2019, total stock-based compensation expense related to unvested options not yet recognized totaled approximately $2.8 million.

Performance Based Stock Options

A summary of the performance based stock options for the six months ended June 30, 2019, is as follows:


			Weighted Average
			Exercise
	Number of Shares		Price
Outstanding at December 31, 2018	388,125	$	4.70
Outstanding at June 30, 2019	388,125	$	4.70

Exercisable at June 30, 2019	-	$	-

Stock-based compensation expense recognized for performance based stock options was $0.1 million and $0.2 million during the three and six months ended June 30, 2019. No stock-based compensation was recognized during the three and six months ended June 30, 2018, since there were no performance based stock options outstanding during that period. As of June 30, 2019, the unrecognized stock-based compensation expense related to performance based stock options was $0.7 million.