Type 304 Stainless Steel sheath provides physical strength and resistance to high temperatures of up to 1200°F (650°C) and chemical corrosion. Helically wound resistance wire coil made from nickel-chrome wire is evenly stretched and precisely strung through the ceramic insulator, providing uniform heat. A custom mixture of several high purity magnesium oxide grain sizes, chosen to increase thermal conductivity and dielectric strength, are used to fill all remaining space inside and around the ceramic insulator. Channel strip heaters are available with or without mounting tabs. If without, the ends are silver soldered shut to prevent moisture and contaminants from entering the heater. The nickel-plated steel fins (SS optional) are mainly used for both forced air in a duct and natural convection air heating in a cabinet type oven.