The British Official Armour Specification is a set of standards for armour construction for armoured fighting vehicles prior to and into World War II. Standards applicable to British tanks of World War II are as follows: * I.T.60: Face-hardened 7 to 12 mm plate. * I.T.70: Thin homogeneous hard 3 to 30 mm plate. * I.T.80: Thick homogeneous-machineable 15 mm and greater plate. * I.T.90: Cast armour of all thicknesses. * I.T.100: Thin homogeneous-machineable 3 to 14 mm plate. * I.T.110: Carbon manganese steel backing plate.