Specially treated rust-resistant steel sheath casing provides physical strength, high emissivity and good thermal conductivity for sheath temperatures up to 900°F (480°C). For corrosive atmospheres stainless steel sheath is available. Specially selected mica grade and thickness is used to insulate the windings, providing excellent thermal conductivity and dielectric strength. A nickel-chrome resistance ribbon wire size is properly engineered to achieve the best combination of wire gauge and spacing between turns, thereby providing the lowest winding temperature possible. The ribbon wire is wound on a specially selected Mica Strip, providing even heat distribution for maximum heater life.