Restricted Stock Units

During the six months ended June 30, 2019, the Company issued 15,000 restricted stock units ("RSUs") to each of its three non-management directors as an annual grant for 2019 for service on the Company's Board of Directors. The RSUs vest in four equal quarterly installments of 3,750 shares of common stock on March 15, 2019, June 15, 2019, September 15, 2019 and December 15, 2019, subject to continued service on the Board of Directors.

During the six months ended June 30, 2018, the Company issued 15,000 RSUs to each of its three non-management directors as an annual grant for 2018 for service on the Company's Board of Directors.  The RSUs vested 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, 2019 is as follows (each restricted stock unit issued by the Company represents the right to receive one share of the Company's common stock):

Restricted stock unit compensation expense was $127,000 and $225,000 for the three months ended June 30, 2019 and June 30, 2018, respectively.  Restricted stock unit compensation expense was $271,000 and $451,000 for the six months ended June 30, 2019 and June 30, 2018, respectively.

The Company has an aggregate of $472,000 of unrecognized restricted stock unit compensation as of June 30, 2019 to be expensed over a weighted average period of .99 years.

All of the Company's outstanding (unvested) restricted stock units have dividend equivalent rights.  As of June 30, 2019, there was $102,000 accrued for dividend equivalent rights.  As of December 31, 2018, there was $76,000 accrued for dividend equivalent rights.

Stock Options

There were no stock option grants during the six months ended June 30, 2019 and June 30, 2018.  The following table presents information relating to all stock options outstanding and exercisable at June 30, 2019:

The Company had no recorded stock-based compensation related to stock option grants for the three months ended June 30, 2019 and June 30, 2018.

The Company had no unrecognized stock-based compensation cost as of June 30, 2019.  The aggregate intrinsic value of options exercisable at June 30, 2019 was $672,000.

During the three months ended June 30, 2019, stock options to purchase an aggregate of 925,000 shares were exercised by executive officers of the Company and a consultant (750,000 shares at an exercise price of $0.83 per share by the Company's Chairman and Chief Executive Officer,  50,000 shares at an exercise price of $1.65 per share by each of the Company's Chief Financial Officer and Executive Vice President and 75,000 shares at an exercise price of $1.65 per share by a consultant). With respect to such options, options to purchase an aggregate of 859,849 shares were exercised on a net exercise (cashless) basis by the Company's Chairman and Chief Executive Officer (750,000 shares), the Company's Executive Vice President (34,849 shares)  and a consultant (75,000 shares) resulting in net shares (after delivery of shares for withholding taxes) of an aggregate of 328,111 issued to the Company's Chairman and Chief Executive Officer, 27,713 net shares issued to the Company's Executive Vice President and 28,824 net shares issued to the consultant.

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.