This rear sight attaches to M16/AR-15 flat top A3 upper receivers.  The sight may be used as a back-up rear sight or a lightweight rear sight to co-witness with red dot or holographic sights.  The sight locks in its upright position, a spring loaded release must be depresed to place the sight in the down position.  The windage is adjustable using a standard A2 windage adjustment drum.  One click allows 0.50 moa change on rifles and 0.65 moa change on carbines.  Constructed of both black oxide carbon steel and black anodized aircraft grade aluminum.