Total stock-based compensation expense recognized in the accompanying condensed consolidated statements of operations for the three months ended March 31, 2019 and 2018 was as follows (in thousands):

	Three Months Ended March 31,
	2019		2018
Stock-based compensation	$	999	$	1,943

During the three months ended March 31, 2019, the Company issued 754,729 restricted stock unit awards to employees. Each such restricted stock award vests 100% in February 2020. The grant date fair value of the restricted stock units was $1.49 with a weighted average grant date fair value per share of $1.49.

During the three months ended March 31, 2019, the Company granted certain employees stock options to purchase an aggregate of 294,900 shares of common stock at a weighted average exercise price of $1.49 per share. The options vest over a four year period. The grant date fair value of these awards is $0.3 million with a weighted average grant date fair value of $1.06 per share, as determined using a Black-Scholes option pricing model.

As of March 31, 2019, there were $8.6 million of unrecognized compensation expense related to restricted stock units and options, respectively, which vest over the vesting period.

As of March 31, 2019, there was $1.2 million of unrecognized compensation costs related to stock options subject to performance conditions. The Company evaluates stock awards with performance conditions as the probability that the performance conditions will be met and uses that information to estimate the date at which those performance conditions will be met in order to properly recognize stock-based compensation expense over the requisite service period.