High-quality performance 4 in insulated flexible duct Made of thickened aluminum foil material and made of high-strength elastic spiral steel wire.The middle is covered with glass fiber insulation layer, which has high temperature resistance, acid and alkali resistance, and flame retardancy. Owens Corning Glass Wool Insualtion Glass wool Insualtion is the safest building material, with high corrosion resistance and thermal insulation,R value: R-4.2. The temperature resistance range is -4 ~454 . Sound absorption and noise reduction insulation The internal structure of glass wool insulationis fluffy and the overall density is large, which can absorb the sound in time,Noise can be reduced by up to 85%. 4 inch insulated flexible duct It can be bent arbitrarily, without rigid elbows, the aluminum foil is self-sustaining and will not retract after installation.It can maintain the flatness in the tube and reduce the wind resistance. Multi Function of the 4 in insulated flexible duct Used for high, medium and low pressure ventilation system without corrosive gas.