LG-639 Lasergrips are a rear-activated laser sight are compatible with GLOCK Compact Gen 1 & 2 19 Gen 3- 19/23/25/32/38 Gen 4-19/ 23/32 Gen 5- 19. Will not fit 19X. Featuring Crimson Trace's famed Instinctive Activation, which allows the laser to be activated with a normal firing grip, the LG-639 includes a Master On/Off Switch for completely powering down the unit. User-installed in moments by attaching securely to the gun frame, this laser sight is fully adjustable for windage and elevation. Provides 4 hours of run time with (2) included 2032 Lithium Batteries.