Yankee Hill Machine Flip Rear Sight For Picatinny Rail, Matte Black. Rugged, 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 measures .840 inches from the highest point down to the top of the upper receiver. It has a 1/2 MOA and comes with a standard rear peep aperture. Mounts to any picatinny rail..