The GG&G A2 Spring Actuated BUIS provides the operator with an easy-to-install push button operated AR 15 flip up sight. The Spring Actuated A2 BUIS can be used as a stand-alone sight or in conjunction with one of our interface rails. It can also be used as a co-witness iron sight with most red dot sighting systems. Weighing in at just over 2.4 ounces, it features the standard military A2-style double peep aperture which allows for end user known point of impact. The AR15 flip up rear sight has full windage adjustment with standard military windage knob and windage screw. No need to retrain. One click of the windage knob provides approximately 0.48 MOA change when mounted on the M16A2E4 rifle and about 0.65 MOA on the M4 carbine. Initial zero is set by adjusting the weapons front sight post. It is low profile so that when in the down position, it will clear most optics. The mount body and sight stem are manufactured from solid billet 6061 T6 aluminum alloy and Type III hard coat anodized in a non-reflective black mil-spec finish to provide combat durability. All steel components are black manganese phosphated per mil-spec.