This specification applies to cast iron fittings of nominal diameters up to 24 inches, cast in moulds. The fittings are intended primarily for use with cast iron pressure pipes for the conveyance of water, gas and sewage, but are also suitable for use with asbestos cement pressure pipes. Provision is made for fittings of Class B, C and D on the basis of wall thickness, but the specification does not imply a correlation between the classes and any particular working pressures.