Wire Wound Element: A fine gauge resistance wire is spiraled around a fiberglass core. The element is placed in a specifically designed pattern and vulcanized to either a silicone rubber or neoprene substrate. Advantages versus etched foil elements are: Physical strength; flexibility; smaller production quantity; conforms well to small radius bends and larger possible sizes. 

Etched Foil Element: The manufacturing process of etched foil elements is adapted from the production of printed circuit boards. A nickel resistance alloy foil is acid etched to the specific pattern, then vulcanized to the sheath material. Advantages versus wire wound are: Higher watt densities; greater area coverage of element over heater sheath; higher production quantities and complex heat distribution.