Nylon is generally supplied in neutral form by chemical companies or, on request, coloured black, with self-extinguishing properties of V2UL 94 guaranteed. All the data analysed above were taken from technical publications issued by primary producers and are generally referred to natural colour nylon. On request, the raw material can be coloured by incorporating pigments that are already available in accordance with the following programme. The pigments utilised are generally inorganic in nature. In special cases organic pigments may be utilised. In all cases, feasibility must be checked colour by colour, with a series of specific tests and checks.