Made of hardened steel, the screwdriver bits in this set are magnetized to remain securely in place in your drill/driver and have been heat-treated for longer life. Their optimized design helps prevent them from slipping out of screw heads. Each bit has a shank diameter of 1/4-inch. The set helps you drive screws straight and quickly, and a pair of magnetic nut drivers to tighten nuts and bolts. Hardened, heat-treated, magnetized steel screwdriver bits| Contains an assortment of Phillips, slotted, and square screwdriver bits, plus magnetic drive guides and magnetic nut drivers| Independently certified to meet industry standards| Includes tough storage case| Compatible with any drill/driver