MC-10 mast clamps secure non-rotating masts to Hazers, Roof-top Towers, and other applications. Each clamp has a mounting flange with four threaded 1/4-20 holes on a 3 1/2 inch bolt circle. Four stainless steel bolts are provide for mounting. The maximum mast diameter is 2 3/16 inches and the minimum diameter is 1 1/4. The mast is secured in place by four 5/16-18 hex bolts which are also provided. Made of cast aluminum. Two MC-10s are generally required, one for the top mount and one for the bottom mount.