As, Oxidized eureka wire wound on a porcelain tube is supported at both ends by durable, cast-aluminum, enamel painted end supports. A plastic sliding contact with laminated phosphor bronze strips is attached to the metallic bar, which in turn is mounted parallel to the tube. Three 4mm socket terminals with captive heads for electrical connection. Designed for Continuos use without overheating. Tolerance in nominal for marked value of resistance is ±5%. Resistance and current rating marked, but with design improvement. Instead of phosphor bronze strip contacts, springs loaded sliding contact of solid brass provided. End supports are larger, sturdier, providing more stability, with grooves to take thick gauge steel, perforated cover.