The NcSTAR Picatinny Riser .625 Cantilever is a 5.5 inch long cantilevered riser rail. The Cantilever desing allows the rail to bridge over the handguards. It allows the user to raise their optic 0.625 inches above their receiver height Picatinny rail for the desired optic height. It's great for a better heads-up shooting with night vision equipment.