The DS-121 Defender Series™ Accu-Guard™ Laser Sight by Crimson Trace fits GLOCK Full-Size and Compact pistols. The Defender Series sets a new standard in laser sight for GLOCK pistols by providing cutting edge design" superior technology" and an affordable price tag. The DS-121 features Beam Lock™ Adjustments so that the user can easily adjust laser sighting for both windage and elevation" and the unit is pre-sighted at the factory at 50 ft. The Dual Side N-Gage™ Activation Buttons provide a large" easy-to-find" bright red activation button" which emits a powerful (5mW peak" 620-670nm" Class 3R) red aiming laser.