The StreamLight ProTac® Rail Mount 1 is a fixed-mount, dual fuel long gun light with a light output of 350 lumens (with CR123A battery power). It is machined from 6000 Series aircraft aluminum with anodized finish. The impact resistant Borofloat® glass lens is high temperature, shock mounted and AR coated. The light source offers C4® LED technology and is impervious to shock with a 50,000 hour lifetime. A TIR optic produces a concentrated beam with optimum peripheral illumination. It can be powered with either (supplied) CR123A or AA Alkaline batteries.