The FBS/RBS are an advanced, dual aperture, durable and low-profile auxiliary sights. They are readily mounted on any 1913 Picatinny rail, making it ideal for use on M4/AR-15/M-16 platforms and on the FAB Defense K.P.O.S.. Made of extremely durable high-grade polymer and metal, the sights features a low folded profile which is smooth and inconspicuous and will not snag on gear, webbing or brush. The instant spring-lockable deployment mechanism will not slip, brake or deform. No tools needed for easy, repaid windage adjustments, with positive detent locking.