The Capri Tools Impact Screwdriver Bits are made of custom high-impact steel, forged specifically for impact screwdrivers. They are designed for Capri Tools 1/2 in. Premium Impact Screwdriver (Model 21095) and fit 5/16 in. hex sockets. The bits are expertly heat-treated for extraordinary strength and durability. Used with an impact screwdriver, they are perfect for applications such as replacing brake caliper where fasteners require extra force to loosen and properly tighten. Set includes 8 impact screwdriver bits: Slotted: 5/16 x 1-3/8, 3/8 x 1-3/8, 5/16 x 3-1/8, 3/8 x 3-1/8 in., Phillips: PH2 x 1-3/8, PH3 x 1-3/8, PH2 x 3-1/8, PH3 x 3-1/8 in.