Stock-Based Compensation - (Tables)

The Company recognized total stock-based compensation expense during the years ended December 31, 2019 and 2018 as follows:

A summary of the Company’s restricted stock awards during the years ended December 31, 2019 and 2018 is as follows:



	Number of Shares		Weighted Average Grant-Date Fair Value
Unvested at January 1, 2018	480,000		$	7.27
Forfeited	(333,200	)	$	5.70
Unvested at December 31, 2018	146,800		$	5.70
Unvested at December 31, 2019	146,800		$	5.70

A summary of the Company’s service based restricted stock units during the year ended December 31, 2019 is as follows:



	Number of Shares		Weighted Average Grant-Date Fair Value
Unvested at December 31, 2018	472,959		$	4.32
Granted	244,063		4.09
Forfeited	(28,916	)	4.32
Vested	(224,320	)	4.19
Unvested at December 31, 2019	463,786		$	4.26

A summary of the Company’s performance based restricted stock units during the year ended December 31, 2019 is as follows:

The following assumptions were used in the model in fiscal year 2018:



Expected stock price volatility	70.0%
Risk-free interest rate	2.9% - 3.1%
Dividend yield rate	—
Term (years)	10.0

The fair value of the service based stock options granted for the years ended December 31, 2019 and 2018 were based on the following assumptions:



	December 31,
	2019	2018
Exercise price	$1.91 - $6.55	$3.17 - $5.75
Expected stock price volatility	67.5% - 70.3%	67.5% - 69.9%
Risk-free interest rate	1.4% - 2.6%	2.7% - 3.2%
Term (years)	3.38 - 6.5	5.0 - 6.5

A summary of the Company’s service based stock option activity for the years ended December 31, 2019 and 2018 is as follows:



	Shares Underlying Options		Weighted Average Exercise Price			Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value
Outstanding at January 1, 2018	6,906,001		$	7.92		5.1	$	976,355
Granted	1,447,479		$	4.55		9.3
Exercised	(267,500	)	$	3.09		—
Forfeited	(229,500	)	$	6.59		—
Outstanding at December 31, 2018	7,856,480		$	7.50		5.2	$	—
Granted	1,103,938		$	3.37		9.0	107,150
Exercised	(30,000	)	$	4.93		—
Forfeited	(720,394	)	$	(6.24	)	—
Outstanding at December 31, 2019	8,210,024		$	7.06		5.1	$	107,150

Exercisable at December 31, 2019	6,481,095		$	7.97		4.1	$	—

The following assumptions were used in the model in fiscal year 2018:



Expected stock price volatility	70.0%
Risk-free interest rate	2.9%
Dividend yield rate	—
Term (years)	10.0

A summary of the performance based stock options granted for the year ended December 31, 2019, is as follows:



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

Exercisable at December 31, 2019	—	$	—

Number of Shares

Weighted Average
Grant-Date
Fair Value

Unvested at December 31, 2018

Unvested at December 31, 2019