The canted 3/4" picatinny riser mount With 5" of rail space, you adds .83" to the height of your mounting rail. If installing an AR-15 rifle scope, two 3/4" Picatinny riser mounts may be required. The AR-15 3/4 inch Picatinny Riser is made from black anodized aircraft grade aluminum and accepts all standard Weaver/Picatinny 1913 accessories. Dimensions: 5" L x 3/4" H. The ¾" Picatinny riser mount is perfect for a flattop AR-15 application, where additional height is often needed to put shooters in a proper position to use optics and sights.