K7936 Flexible Duct For Nominal Duct Diameter 4 in Wall Thickness 2.5 in Maximum Temperature Rating 140 Degrees F Insulation Value R 8.0 Duct Material Fiberglass Fire Rating Flame Spread/Smoke Developed-Less Than 25/Less Than 50 Maximum Pressure Rating 6 in wc Vapor Transmission 0.6 Standards UL181 NFPA 90A and 90B IMC IRC UMC 10-1 (ICC ES Report No ESR-1268) HUD Cities of Chicago New York San Francisco County of Dade (Florida) California State Fire Marshall Material Polyester