LMS-1151FGR fits all Current production FGR (Weaver Rail) guns and G21SF. LaserMax is the leading manufacturer of laser gunsights for law enforcement and the shooting sports community. The LaserMax is the prime choice for law enforcement and special operations and firearms training, as well as home defense, target shooting and hunting. The LaserMax is universally acknowledged as the top laser sight for quality and reliability. Installation Takes 5 Minutes - no gunsmithing required! Almost instantly you'll have a laser-sighted weapon which can be used outdoors from dusk till dawn, or indoors round-the-clock. Drops into place (replaces original recoil spring guide). Unit cannot be knocked out of alignment, deliberate on/off activation. Made in U.S.A. Three-year warranty (excludes expendable parts). Additional Features: Laser Operating Temperature is 15 - 120F Wavelength: 635nm (red-orange) Power Output: 3mW (brightest available - pulsates for highest visibility) Water proof to 66 feet