Ideal for use in general ventilation applications including heating, air conditioning, intake and exhaust. UL 181 listed as a class 1 air duct and bears the UL mark. Consists of a flexible helix core made of 2 ply polyester laminate and corrosion resistant galvanized wire. Surrounded by a blanket of formaldehyde free, fiberglass insulation, that helps to reduce heat and cool loss as well as jacketed by a heavy duty, fire retardant, black polyethylene vapor barrier. Can be installed in place of galvanizedpipe in most applications. R-4.2 insulation value.