"Looking for rock solid stability and dead-on accuracy in a fixed sight? Troy Industries Fixed BattleSights? 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. Features: A permanent rail mounted alternative to a standard A2 rear sight or carry handle. Provides constant access to fixed sights that continuously hold their zero. Extremely durable and reliable providing peace of mind. The most rugged fixed rear sight available. Fits all M4, M16, AR15, AR10 variants and other firearms that have a flat top receiver or removable carry handle. Machined from hardened Aircraft Aluminum with stainless steel components and finished in MIL-SPEC hardcoat anodizing. 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. 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.