Bright flashlight and powerful integrated laser. It has a built-in on/off switch It is designed to mount on any standard weaver rail on a pistol or rifle. Compatible with all pistols and rifles with standard rails such as Umarex T4E Walther PPQ, Umarex T4E TPM1 Glock, Umarex T4E Smith and Wesson M&P, Umarex T4E HDP Home Defense Pistol, HDR 50 TR50 Revolver, HDS Shotgun Uses 3V Lithium Batteries CR123 CR123A, DL123, 123, EL123, CR17345 Note: Positive terminal end goes toward spring. *Battery is not included