Crimson Trace Corporation LaserGrip, Fits Glock Gen3 17/22/31/34, Black 01-6710-1 LG-637 Lasergrips(R) are a rear-activated laser sight for GLOCK Full-Size pistols (Third Generation 17" 17L" 22" 24" 31" 34" 35" 37" Gen4 17" 22" 31" 34" 35" 37 and Gen5 17" 19X" 45). Featuring Crimson Trace's famed Instinctive Activation(TM)" 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.