The Quick Fist XL clamp holds objects up to 15” (381mm) in diameter or about 30” (762mm) in a linear direction. Some objects may require 2 sets to mount securely. The Quick Fist XL clamps are not only our largest size, but they are also our strongest clamp. They provide a safe working load of 150lbs (68kilos), and a break-strength of 300lbs (176kilos) per clamp. Two clamp sets support up to 600lbs (273kilos).