Durability and dead-on accuracy make Troy BattleSights(TM) the hands-down first choice of Special Ops and Tactical Users Worldwide. Troy's M4 Front Fixed BattleSight, a permanent, rail-mounted alternative to a standard A2 sight, allows limitless mounting options on all-length rails with a serrated ramp. Features: Sight can be moved or taken off without permanent modification to the firearm. Snag-free apertures at factory height. Designed to work on same-plane rail systems only. (NOTE: 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 the receiver height will not zero properly.)