ProMag AR-15/M16 A2 Dual Aperture Flip-Up Rear Sight, Black Can be used as a co-witness iron sight with most red dot and holographic sights, or as a stand-alone sight Features the standard military A2-style double peep aperture Has full windage adjustment Steel parts are CNC machined, then black phosphate per mil-spec Mounted to the rail via a locking bar and secured with a cross slotted, knurled thumb screw