FOR GEN 4 MODEL 20, 21, 41 Designed specifically for use in Glock 20 (Gen4), Glock 21 (Gen4), and Glock 41 (Gen4) pistols, the LMS-G4-1151G replaces Glock's factory spring guide assembly with a high intensity green laser sighting system for advanced target acquisition. Easily user installed without the need for gunsmithing or special tools, the Guide Rod Laser is constructed with rugged, precision components including aircraft-grade aluminum and genuine Wolff springs. Pulses for superior visibility and faster identification Internal design does not restrict grip or holster selection Distinct ambidextrous ON/OFF switch reinforces safe firearm handling Proximity to the bore provides maximum POA/POI accuracy Guaranteed alignment ensures center of mass shots