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: PZ2 Length mm: 100 Shank Dia. inch: 1/4 Shank Type: Hex Material: S2 Hardened Carbon Steel Timco S2 Driver Bits - PZ (Size No.2 x 100 - 1 Each) in Silver