Yankee Hill's Flip Rear Rifle Sight features a rugged but lightweight design with a steel base, a quick release thumb screw, and aluminum stem. Locks in the deployed position with ease and takes up very little space on the upper receiver. When folded it only measures .840 inches from the highest point down to the top of the upper receiver. It has a 1/2 M.O.A. and comes with a standard rear peep aperture. Mounts to any picatinny rail. Designed to co-witness with the standard M16-M4 front sight and all of our front sights.