GZ25903 | Groz Number Punch Set 4mm Manufactured from quality carbon steel. Punches are induction hardened which gives durability and extended life for repeated use. The hardness at the stamping end is maintained at 58-62 HRC the striking end is tempered to 38-43 HRC. This prevents the punch from splintering during use. The striking end is chamfered to prevent breakage. Specification Size: 4mm