The MBUS (Magpul Back-Up Sight) is a low-cost, color injection molded, folding back-up sight. The MBUS Front Sight is adjustable for elevation and fits most 1913 Picatinny-railed hand guards, but is specifically tailored to the AR15/M16 platform.Features : Spring loaded flip up sight Easily activated from either side or by pressing the top Protective wings shield the spring-locking A2 front sight post Polymer construction provides light weight and resists abuse Detent and spring pressure keeps sight in place but allows for unobstructed folding under impact