LG-637 Lasergrips are a rear-activated laser sight are compatible with GLOCK Full Size Gen 3- 17/17L/22/24/31/34/35/37 Gen 4-17/ 22/31/34/35/37 and Gen 5-17/19X/45. Featuring Crimson Trace's famed Instinctive Activation, which allows the laser to be activated with a normal firing grip, the LG-637 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.