Use these cantilever mounts for mounting magnified optics onto flattop AR style rifles. The 2" and 3" offset of these cantilever mounts position the scope further forward, allowing the correct eye relief and head placement on AR style rifles. Aluminum construction. 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. Mfg: Vortex Optics