MAGPUL MBUS Flip-Up Rear Sight AR15/M4 Black\n\nThe MBUS (Magpul Back-Up Sight) is a low-cost, 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.\n\nFeatures:\n- Impact resistant polymer construction provides light weight and resists operational abuse\n- Spring-loaded flip up sight easily activated from either side or by pressing the top\n- Detent and spring pressure keeps sight erect but allows for unobstructed folding under impact, etc.\n- Clamps to MIL-STD-1913 Picatinny/STANAG 4694 receiver rail and provides the same height-over-bore as standard A2 irons\n- Protective wings shield the dual, same plane flip apertures\n- Sight can still be folded with either large or small aperture in position\n- Detent knob easily and positively adjusts windage\n\nSpecifications:\n- Weight, w/ hardware: 1.3 oz.\n- Height above rail, stowed: ~0.51 in.\n- Center of aperture to top of rail: 1.42 in.\n- Length, stowed: 2.6 in.\n- Length, deployed: 1.5 in.\n- 0.754 inches per 100m per click with a 14.5" sight radius\n- 0.547 inches per 100m per click with a 20" sight radius