These ball socket head screws have a round or flat ball ends. The ball rotates in the screw socket as force is applied allowing contact to be maintained on moving or contoured surfaces as force is applied. The screw is made from 4135alloy steel with a black oxide finish. The ball is made from 52100 alloy steel and hardened to Rc 56-60. These screws are used on CP100/101/102 series clamps, and BJ350/351 work supports.