Abstract: Wire or cable insulation comprising at least 30%, preferably at least 40%, of polypropylene homo- and/or co-polymer, and comprising at least 2%, preferably at least 4% zinc sulphide and/or at least 5%, preferably at least 10%, zinc oxide, percentages being by weight based on the whole insulation composition. preferably, the insulation contains little or substantially zero hydrated flame-retardant fillers and substantially zero mercaptobenzimidazole, and a majority by weight or substantially all of any propylene copolymers present are copolymers of propylene with halogen-free co-monomers.