The DS-121 Defender Series(TM) Accu-Guard(TM) 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(TM) 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(TM) 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.