Troy Industries SSIG-FBS-FHBT-03: Durability and dead-on accuracy make Troy BattleSights the hands-down first choice of Special Ops and Tactical Users Worldwide. Troy\'s HK 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. NOTE: Will not work with a railed gas block that is higher or lower than the receiver.