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 .223 platform. Features: Impact resistant polymer construction provides light weight and resists operational abuse. 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 MIL-STD-1913 Picatinny/STANAG 4694 receiver rail and provides the same height-over-bore as standard A2 irons. Protective wings shield the dual, same plane flip apertures. Sight can still be folded with either large or small aperture in position. Detent knob easily and positively adjusts windage. Specifications: MBUS – Front/Rear Gen 2. Weight, w/ hardware: 1.3 oz. Height above rail, stowed: ~0.51 in. Center of aperture to top of rail: 1.42 in. Length, stowed: 2.6 in. Length, deployed: 1.5 in. Made in U.S.A. UPC Code: 873750004358. Manufacturer: Magpul Industries. Model: Generation 2. Model: MBUS. Type: Sight. Fit: Picatinny. Finish/Color: Black. Description: Rear. Manufacturer Part #: MAG248-BLK. UPC Code: 873750004310. Manufacturer: Magpul Industries. Model: Generation 2. Model: MBUS. Type: Sight. Fit: Picatinny. Finish/Color: Black. Description: Front. Manufacturer Part #: MAG247-BLK.