The die-cast aluminum  6" Super Viser Clamp from Kupo securely grabs onto round or flat surfaces, such as tubes or boards, up to 6". The knurling on the handle maximizes friction, allowing you to loosen and tighten the clamp more easily, and  the specialized grooved design on the threaded shaft helps keep the jaws properly aligned during use. There is a 16mm mounting pin at the end of the shaft and integrated 16mm socket. The socket makes the Super Viser Clamp compatible with all your favorite Convi Clamp accessories, thereby enhancing its utility.