K7936 Flexible Duct For Nominal Duct Diameter 8 in Wall Thickness 2.5 in Maximum Temperature Rating 140 Degrees F Minimum Temperature Rating -20 Degrees F Insulation Value R 8.0 Color Gray Overall Length 25 ft Duct Material Fiberglass Jacket Material Polyester Fire Rating Flame Spread 25 Max Smoke Developed 50 Max Maximum Pressure Rating 6 in wc Maximum Air Speed 5 000 fpm Vapor Transmission 0.6 Percent