Abstract: A cartridge heater, wherein the terminal lead pins which project from the terminal end of the heater at the outer surface of the electrical insulating end plug, are substantially reduced in length and provided with at least one flat planar surface on what was originally the cylindrical surface of each lead pin. The terminal ends of the external flexible lead wires are then fused to the flat surfaces on each of the lead pins by means of brazing, soldering or welding. An end adapter unit having two longitudinal bores is then threaded up over the two flexible lead wires until the outer casing, which encloses an electrical insulating core having the two circular bores for the flexible wires, is telescoped over the terminal end of the cannister which encloses the cartridge heater.