Restricted Stock Units

During the six months ended June 30, 2018, the Company issued 15,000 restricted stock units to each of its three non-management directors as an annual grant for 2018 for service on the Company's Board of Directors.  Each restricted stock unit represents a contingent right to receive one share of the Company's common stock.  The restricted stock units vest in four equal quarterly installments of 3,750 shares of common stock on March 15, 2018, June 15, 2018, September 15, 2018 and December 15, 2018, subject to continued service on the Board of Directors.

A summary of restricted stock unit activity for the six months ended June 30, 2018 is as follows (each restricted stock unit represents the right to receive one share of the Company's common stock):

Restricted stock unit compensation expense was $225,000 and $237,000 for the three months ended June 30, 2018 and June 30, 2017, respectively, and $451,000 and $474,000 for the six months ended June 30, 2018 and June 30, 2017, respectively.

The Company has an aggregate of $526,000 of unrecognized restricted stock unit compensation as of June 30, 2018 to be expensed over a weighted average period of 1.39 years.

All of the Company's 772,500 outstanding (unvested) restricted stock units at June 30, 2018 have dividend equivalent rights.  As of June 30, 2018, there was $113,000 accrued for dividend equivalent rights.  As of December 31, 2017, there was $84,000 accrued for dividend equivalent rights.

Stock Options

There were no stock option grants during the three and six months ended June 30, 2018 and June 30, 2017.

The following table presents information relating to all stock options outstanding and exercisable at June 30, 2018:

The Company had no recorded stock-based compensation related to stock option grants for the three and six months ended June 30, 2018 and June 30, 2017.

The Company had no unrecognized stock-based compensation cost as of June 30, 2018.  The aggregate intrinsic value of options exercisable at June 30, 2018 was $3,143,300.

During the three months ended June 30, 2018, a director of the Company exercised on a net exercise (cashless basis) a stock option to purchase 300,000 shares of common stock, at an exercise price of $1.88 per share, which resulted in net shares of 118,064 issued to the director.  During the three months ended June 30, 2017, no stock options were exercised.

Warrants

As of June 30, 2018, there were no outstanding warrants to purchase shares of the Company's common stock.

During the six months ended June 30, 2017, Recognition Interface, LLC exercised its remaining warrants to purchase an aggregate of 375,000 shares of the Company's common stock, at an exercise price of $2.10 per share, which resulted in gross proceeds to the Company of $787,500.