Robust screw tightening! Chrome-molybdenum steel for high torque resistance. You can use the PRO Impact socket set for hex screws, bolts, and nuts with your square-drive wrench. We designed it for screwdriving tasks during extensive assembly work or other demanding industrial applications. The PRO Impact socket set is made of heat-treated CRMO (chromium-molybdenum) steel and, thanks to its thick walls, is highly resistant to high torque. The black phosphate coating protects it from rust and corrosion. The sockets are laser-marked and color-coded so you can find the right one at a glance. They feature a keyway and a through-hole. For extra-strong grip, they can be attached to your impact wrench with the included pin and ring.