Made in the USA, 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.Features- spring-loaded flip up sight easily activated from either side or by pressing the top, detent and spring pressure keeps sight erect but allows for unobstructed folding under impact, etc.; clamps to most any MIL-STD-1913 Picatinny/STANAG 4694 railed hand guard and provides the same height-over-bore as standard A2 irons and protective wings shield the spring-locking A2 front sight post. Includes elevation adjustment tool, but most aftermarket A2 front sight adjustment tools may be used. *NOTE: 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.