Designed for square drives - You can use the PRO Impact socket set for hexagon head screws, bolts and nuts with your square drive spanner. It has been developed for screwdriving work on extensive assemblies or other demanding industrial work. The PRO Impact socket set is made of heat-treated CRMO (chrome-molybdenum) steel and is highly resistant to high torques thanks to its thick walls. The black phosphate coating protects it from rust and corrosion. The sockets are laser-marked and colour-coded so that you can find the right one at first glance. They have a groove and a through hole. They can be attached to your impact wrench with a pin and ring for an extra-strong hold.