THHN/THWN PVC Insulated / Nylon Jacketed Wires are heat, moisture, oil & gasoline-resistant American Building Wires. alfanar THHN/THWN building wires are engineered for reliable performance in residential, commercial, and industrial electrical installations. Designed to withstand demanding environments, these wires offer exceptional resistance to heat, moisture, oil, and gasoline—making them a trusted choice for modern electrical systems. THHN/THWN wires are used for general-purpose power and lighting circuits and are suitable for installation in ducts, conduits, and raceways in both wet and dry locations. They meet multiple industry classifications, including: 1. THHN – Rated 105°C for dry locations, ideal as building wire. 2. THWN – Rated 75°C for wet locations; suitable for building wiring. 3. MTW – Rated 90°C for dry and 80°C for wet locations; commonly used as machine tool wire. 4. TFFN – Rated 105°C for dry locations, flexible cord and fixture wiring.