The MBUS (Magpul Back-Up Sight) is a low-cost, polymer, 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. Spring-loaded flip up sight easily activated from either side or by pressing the top release. Protective wings shield the spring-locking A2 front sight post. Provides the same height over bore as standard A2 sights. 1.6 MOA (1.886″/100m) per click with 14.5″ sight radius. 1.2 MOA (1.367″/100m) per click with 20.0″ sight radius. Cannot be mounted to a railed gas block due to excess heat issues. Front MBUS must be mounted to a railed fore end on the same plane as the receiver rail. Because of this the sight is also not compatible with MOE Hand Guards. Made in the USA.