Designed specifically for use in Glock 20, 20SF, 21, and 21SF pistols, the LMS-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.