Copper THHN/THWN has a Solid or Stranded Copper conductor with a Thermoplastic High-Heat (THH) & Water (THW) Resistant PVC insulation and a Nylon (N) jacket. It is primarily used in low voltage applications up to 600 volts for locating buried gas, water, sewer, electric and telephone lines in commercial, industrial or residential applications. The wire should not be used in areas with temperatures exceeding 90°C.