The Company estimated the fair value of warrants using the Black-Scholes option pricing model. There were no warrants issued in the year ending December 31, 2019 or 2018. A summary of warrant activity for the year ended December 31, 2019 is as follows (shares in thousands except per share and contractual term):

The warrants outstanding at December 31, 2019 had an intrinsic value of approximately $446,000 based on a per-share stock price of $3.08 as of December 31, 2019.