For sale: NONE!! AR-15/M16 USGI backup iron sight.MATECH brand iron sights. These are current US ARMY issue for M4 carbine. Turning a knob changes elevation to eight different settings 200, 300, 350, 400, 450, 500, 550, and 600 meters. Windage adjustment is just as easy. These sights show some wear but are fully functional, stay down, and flip-up. SOLD OUT!!!!!!!!!!