Troy Industries Tritium BattleSights 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. 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. Sight can be moved or taken off without permanent modification to the firearm, snag-free apertures at factory height. Sight is designed to work on same-plane rail systems only. Sight 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. Railed gas blocks that are lower than receiver height will not zero properly.