Made of polymer plastic, very light weight Package Include: 1 set of 4 pieces - enough for 2 mounts ("adapters" only - not mounts.) Pack of 4 pieces for 2 rings Converts 30mm Rings to 1" Split design for easy installation 5/8" 16mm wide Scope Ring Reducer Spacer Split design for easy installation Light weight, small and easily carry Converts 30mm Rings to 1" 5/8" 16mm wide Fit to 30mm diameter scope rings