Matech USGI Folding BUIS (Back Up Iron Sight)
Current U.S. Army standard-issue backup rear sight for M4 carbines and M16A4 rifles flips up instantly at the touch of your thumb when primary sight fails or tactical situation makes iron sights preferable. Designed for effective targeting out to 600 meters. Detent-locking lever lets you quickly switch to one of eight range settings: 200, 300, 350, 400, 450, 500, 550, and 600 meters. Adjust windage easily with grooved, A2-style windage knob and position markers on the back of the sight for repeatability of settings. Bright, white, laser etched numbers and markers are clearly visible even in low light. Rugged machined steel construction ensures sight retains zero even under heavy, full-auto fire. Clamps securely to the rearmost slot of MIL-STD 1913 Picatinny or Weaver-style accessory rail on flattop receiver via simple but strong locking bar and bolt. Rounded corners and beveled edges further reduce danger of snagging on other gear when sight post is down. Regulates correctly with A2 front sight on any AR-15-style rifle or carbine. Designed to co-witness with most non-magnifying optical sights.