S2 Steel is premium quality alloy steel for exceptional strength and durability compared with stan...S2 Steel is premium quality alloy steel for exceptional strength and durability compared with standard chrome vanadium driver bits. S2 grade hardened steel for longer life"Driver Bit Size: PZ2Length mm: 100Shank Dia. inch: 1/4Shank Type: HexMaterial: S2 Hardened Carbon Steel.