The MBUS (Magpul® Back-Up Sight) is a low-cost, color injection
molded, folding back-up sight. The dual aperture MBUS Rear Sight is
adjustable for windage and fits most 1913 Picatinny rail equipped
weapons, but is specifically tailored to the AR15/M16 platform. Made in U.S.A.
MBUS – Rear