The RAM Rail Mount consists of a locking tooth system with a standard RAM diamond plate end. The mount will fit a rail diameter from 1.0″ to 1.1″. To mount to a circular rail, simple press the composite U clamp around the rail and then connect and tighten the small nut and bolt to close the U clamp. Next connect the diamond plate to the mounted clamp at the required angle and screw in the other bolt through the diamond plate. Now you are ready to connect any of the RAM Composite HOL Cradles or any other cradle with two holes positioned 1.912″ center to center. Placing a rubber lining (not included) between the tube and the mount for a tube with a diameter less than 1″ will help the base grab the rail. NOTE: You cannot rotate the diamond plate on the U clamp when the cradle is connected.