Hardened nail specifically designed for fixing to masonry and concrete blocks. Corrosion Rating1 -...Hardened nail specifically designed for fixing to masonry and concrete blocks. Corrosion Rating1 - Clean, dry & low humidity environments. Finish: Zinc. Head Type: Flat. Length: 30mm. Material: Hardened Carbon Steel. Product Code: HM25030. Shank Dia.: 2.50mm. Substrates: Masonry.