n An electrical heating unit shaped to fit extruder barrels, adapters, die surfaces, etc, for maintaining high temperatures of the banded items and furnishing heat to the plastics within them. Nichrome wires within the bands are embedded in insulation such as magnesium oxide and their ends are welded to screw-type terminals at the end of the band. The ends of cylindrical bands are brought together by Monel bolts to tighten them snugly against the surface to be heated. Service life is greatly increased by operating them at 80% or less of rated wattage, the usual practice. See also Cast-in Heater.