Abstract: An induction heater (1) includes a substantially cylindrical jacket adapted to be placed around an article which is to be induction heated, an induction coil (5) arranged within the jacket, and protuberances (4) projecting inwardly from the internal surface of the jacket to keep the article spaced apart from the surface so as to avoid abrasion of the surface by the article. The protuberances (4) may be axially extending ribs, and may incorporate a device, such as an embedded layer, to provide a change in the visible color thereof when worn down. A multipart construction is given for the heater, in which the coil (5) is wound onto an inner former (2) and outer shells (6) are located over the coil.