For use on Glock 20/21/20SF/21SF (Gen 1-3) Pulsating laser sight for faster target acquisition and re-acquisition Extremely rugged lightweight and completely internal Installation takes minutes with no gunsmith help needed No alignment needed Keep your holster - keep your tactical lights - keep your favorite grips; Class IIIa Laser Product: &lt;5mW power output Class IIIA laser, &lt;5mW power output