SPORT CANTILEVER MOUNT - 3-Inch Offset Use this cantilever mount for mounting 1-inch telescopic sights onto flattop style AR-15 rifles. The 3-inch offset of this cantilever mount positions the scope in a forward location, allowing the correct eye relief and head placement on an AR-15. Aluminum construction. Note The cantilever ring mount positions the center of the riflescope tube at a height of 1.59 inches (40.39 mm) from the base. Weighs 6.7 ounces.