The ARMS #71 Flip Up Rear Sight fits all AR15 / M16 rifles with a “flat-top rail” Upper Receiver. Its durable, metal-reinforced polymer construction offers both economy and precision. Height is .600” from the top of the rail when in folded position. A spring loaded mechanism deploys the sight quickly when its forward locking latch is depressed, and the #71-Rear features the same windage adjustable metal dual apertures utilized in the A.R.M.S. #40L.