Brownells' 360-degree rotating backup rear backup sight helps AR-15 shooters achieve proper elevation at a variety of distances. The rotating drum design allows for close-range, 100-, 200- and 300-yard shots. The drum features a large 0.16-inch aperture for close-range shots and three 0.07-inch apertures each regulated for its specific range. Designed for use with any standard-height front sight, the rotating rear sight folds out of the way when not in use. The sight's deeply grooved knob and ball-detent lock provide shooters with precise windage adjustments. Additionally, a large slotted hex nut and locking bar system securely clamps the sight in place and ensures sight repeatability, even during the harshest tactical conditions.