Set it. Forget it. Use this Vortex Cantilever 30mm Mount with 3" Offset to attach your scope of choice to your AR and enjoy reliability shot after shot. Once you get zeroed, your point of impact simply won't shift. Easy to install, just slap it on the rail and torque the screws. 3" offset positions scope in a forward location, allowing for correct eye relief and head placement Positions center of scope at height of 1.59" (40.39mm) from base 1": 2.52" between rings, 6.77"l., weighs 7 oz. 30mm: 2.52" between rings, 6.77"l., weighs 6.75 oz.