Large jaw offers more clamping surface. Jaw moves downward and forward as the clamp is tightened. Allows for quick removal and insertion of parts. Body and jaw are made from 4140 alloy steel, quenched and tempered, with a black oxide finish. Smooth jaw is precision ground. T-slot nut is made from 1045 steel with a black oxide finish. Socket head cap screw is made from 4135 steel with a black oxide finish.