TROY Industries BattleSight, Rear Fixed Sight, Fits Same Plane Rail Systems Only, Picatinny, Black Finish SSIG-FRS-R0BT-00 Looking for rock solid stability and dead-on accuracy in a fixed sight? Troy Industries Fixed BattleSights(TM) get the job done. This permanent" rail-mounted alternative to a standard A2 sight allows limitless mounting options on all-length rails with a serrated ramp to eliminate glare. Provides a continuous zero" unflinching durability and peace of mind. The Troy Rear Fixed Rail Sight is designed to work on same plane rail systems only. Will not work with a railed gas block that is higher or lower than the receiver.