These unique clamps provide very quick and secure fastening for repetitive machining operations. They consist of a clamp base along with a customized pin based on the thickness of the part you are clamping. By turning the handle 1/4 turn, the base clamp pulls the pin downward and secures it in position. Four screws and two locating holes allow for secure fastening and precision locating. Recommended workpiece tolerance is +/-.3 mm for the 150 model and +/-.5 mm for the 200 model. The body and cam made from 4140 alloy steel, heat treated with a black oxide finish. The handle shaft made from 1045 alloy steel with a black oxide finish. The ball knob is plastic.