Troy Industries Tritium BattleSights(TM) are designed to eliminate the poor sight orientation that is typical in twilight. Tritium is a form of hydrogen that emits a continuous light source when batteries or electricity are not available. The front post is centered between two Tritium points of reference to allow proper alignment. Troy Rear Folding Tritium Sights, a permanent, rail-mounted alternative to a standard A2 sight, allow limitless mounting options on all-length rails with a serrated ramp to eliminate glare.Features : Sight can be moved or taken off without permanent modification to the firearm Features snag-free apertures at factory height Front post is centered between two Tritium points of reference Will not work with a railed gas block that is higher or lower than the receiver Front sight must be mounted at the same height plane as the rear sight