The RBS Rear polymer Back-up sight is a cutting edge, low-profile, tactical back-up sight.The dual aperture RBS rear sight is windage adjustable and can be mounted on all 1913 picatinny rails, but is specialty made for the M4 / AR-15 / M-16 platform and the K.P.O.S.Advantages:Very low profile & slim designCan be used as primary or back-up sightState-of-The-art ergonomic & ambidextrous designAll manual configuration, no tools needed for windage adjustmentsDurable high grade polymer & metal constructionSpring based locking mechanism - will not break or deform