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. #471 has fiberglass reinforced metalized cover. Rated R-4.2. Operating temperatures            (-29° to +121°C). Meets UL 181, NFPA 90A and 90B.