Thermo-efficient insulated Heating & A/C Duct. Black CPE Core (bonded to coated wire helix) easily expands over fittings & supports thick blanket of fiberglass insulation. #470 has tough polyethylene cover for Double Air Seal. Rated R-4.2. Operating temperatures (-20° – +250° F). Meets UL 181, NFPA 90A and 90B.