These No.1 PZ-type impact screwdriver bits are made from S2 steel, which is correctly hardened and tempered for durability and long life. Each has a blackened 1/4" hex shank with a shot blast finish and precision ground tips to prevent cam out and screw damage. The shock absorbing torsion design increases torque performance. There are highly visible laser-etched size markings on the hex shank. Specifically designed for use with an impact driver.