10. SHARE-BASED COMPENSATION

On May 19, 2021, stockholders approved an amendment to the 2015 Equity Incentive Plan (the “2015 Plan”) to increase the number of shares available for issuance by 2,000,000 shares.

Restricted Stock Awards. On May 19, 2021, the Company issued to non-executive members of its Board of Directors, as compensation for their annual service, a total of 31,512 restricted shares under the 2015 Plan with a one-year vesting period. Additionally, the Company issued 69,975 performance-based shares in January 2021 and a total of 20,750 performance-based shares to three of the Company’s executives in May 2021. The vesting for these performance-based shares is based on the compounded annual growth rate of the Company’s Adjusted EBITDA and Free Cash Flow Per Share, as defined, for the three-year periods ending December 31, 2021, December 31, 2022, and December 31, 2023. For the 2021 period, one-sixth of such performance-based shares will vest on the anniversary date of the award if the Company’s annual Adjusted EBITDA for 2021 reflects at least 10% per annum growth since 2018, and one-sixth of such performance-based shares will vest on the anniversary date if the Company’s annual Free Cash Flow Per Share for 2021 reflects at least 12% per annum growth since 2018. Vesting of the performance-based shares is similar for the 2022 and 2023 periods.

As of June 30, 2021, the Company had 1,725,478 share-based awards authorized by shareholders and available for grant from the 2015 Plan.

The following table summarizes information related to the Company’s common stock options as of June 30, 2021:

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Share-based compensation expense totaled $199,000 and $103,000 for the three-months ended June 30, 2021 and 2020, respectively, and $323,000 and $186,000 for the six-months ended June 30, 2021 and 2020, respectively. The expense for 2021 includes restricted shares issued to non-executive members of the Company’s Board of Directors as compensation for their annual service, and includes estimates for certain performance-based shares that were issued to the Company’s executives as noted above.

As of June 30, 2021, there was approximately $1.9 million of unrecognized compensation cost related to unvested stock options previously granted that is expected to be recognized over a weighted-average period of approximately 2.5 years.