The Mil-Spec Mepro M21 Self-Illuminated Reflex Sight is used and trusted by militaries and law enforcement agencies worldwide. It is specifically unique in that no batteries are needed. Illumination of the point of aim reticle is achieved by a fiber optic collector system during the day and by a miniature self- powered tritium light source at night. A large 30 mm display window allows the shooter to keep both eyes open for better battlefield situational awareness.With Meprolight everything you aim for. Mepro M21 is the reliable choice. Designed and manufactured the highest military standards to assure years of reliable operation under all field conditions. With no switches no battery or other external sources of power the sight is always ready for action.Features / SpecsBattery: NoneMagnification: 1xObjective: 30mmField Of View: UnlimitedEye Relief: UnlimitedDot Size: 5.5 MOALength: 4.50"Weight: 13.10 ozFinish: BlackReticle: Illuminated DotProofs: Weather Resistant