The Foam Core Spiral Duct Insulation consists of two highly reflective layers of film (96-percent reflectivity) The inner layer of insulating foam core resists conductive heat flow while a center layer of polyethylene give our product high reliability and strength (nominal thickness 5/16-Inch) The product is an ideal alternative to other types of fibrous insulation products for attics, crawl spaces, metal building, garage doors. etc Ease of handling and quick installation make our Duct Insulation the first choice for insulating round or rectangular ductwork A thermal benefit of R-8 is gained when installed directly to the duct Measures 2FT x 5ft foil foam. Thickness 1/4 inch (nominal 3/8-5/8's) Contact Temperature Range: -60°F To 180°F (-51°C To 82°C) • Only Energy Star Rated Foam Core.