For Hand Held Hammer struck applications GROZ Letter and Number Stamps are manufactured from selected quality carbon steel. Punches are through 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 and accidents due to flying splinters The Number Punch Set Contains 9 Pieces: 0 - 9. Numbers 6 & 9 are interchangeable.