Krypt Wakeboard Tower Round Tubing Rack Clamp, Bracket, Surfboard, Wakesurf, Kneeboard, Slalom Ski Wakeboard Tower Rack Clamp Available Sizes: 1 1/4", 1 1/2", 1 5/8", 1 3/4", 1 7/8", 2", 2 1/4", 2 3/8", 2 1/2" 6061 Polished Aluminum w/ 4 Base Holes Threaded or No Thread Fits Most Racks w/ 4 Hole Back Plates.