Durable hardened 40CR alloy steel construction. Suitable for use on Phillips & Pozi head screws. Quick change 1/4″ hex shank. Supplied with storage case. Contents:. 1 x #0 (up to 5mm head). 1 x #1 (up to 6mm head). 1 x #2 (up to 10mm head). 1 x #3 (up to 12mm head). 1 x #4 (up to 14mm head).