| Year ended December 31, 2017 | Options | Weighted average exercise price |
||||||
| Balance, beginning of period | 1,387,000 | $ | 2.37 | |||||
| Granted | 476,000 | 7.20 | ||||||
| Exercised | (207,950 | ) | (2.50 | ) | ||||
| Forfeited, cancelled or expired | (52,923 | ) | (8.58 | ) | ||||
| Balance, end of period | 1,602,127 | $ | 3.58 | |||||
| Options exercisable, end of period | 1,231,127 | $ | 2.50 | |||||
Changes in the number of options outstanding during the years ended December 31, 2016 and 2015 are as follows:
| Year ended December 31 | 2016 | 2015 | ||||||||||||||
| Options | Weighted average exercise price |
Options | Weighted average exercise price |
|||||||||||||
| Balance, beginning of period | 2,277,126 | $ | 1.90 | 1,720,253 | $ | 2.12 | ||||||||||
| Granted | 265,025 | 6.16 | 644,070 | 2.65 | ||||||||||||
| Exercised | (1,069,434 | ) | (1.72 | ) | (23,350 | ) | (1.42 | ) | ||||||||
| Forfeited, cancelled or expired | (85,717 | ) | (9.59 | ) | (63,847 | ) | (15.60 | ) | ||||||||
| Balance, end of period | 1,387,000 | $ | 2.37 | 2,277,126 | $ | 1.90 | ||||||||||
| Options exercisable, end of period | 1,387,000 | $ | 2.37 | 2,277,126 | $ | 1.90 | ||||||||||