The MEPRO 21 reflex sights by Meprolight feature battery-free dual illumination. The massive 30mm objectiv offers an unobstructed view when shooting with both eyes open. The sight is powered by a fiber optic collector in bright stipulations and a tritium light supply in low-light stipulations. The short unlock picatinny rail mount permits for speedy attachment to rail-provided firearms. Also designed to work with a red-dot magnifier. Features a neoprene protecting cover.