This Imperial insulated flexible duct is ideal for use with heating, ventilation, and air conditioning systems. Its 2-ply polyester laminated inner core is constructed with supportive, non-corrosive coated wire. A blanket of fiberglass insulation surrounds the core which helps to reduce heat loss and condensation, and a silver metalized outer jacket with reinforced scrim surrounds the fiberglass insulation for durability. Because of its flexible nature, this duct can be installed in hard-to-reach areas without the need for elbows. The easy-to-install flexible polyester duct is intended for use wherever UL 181 class 1 air duct is required. It measures 14-in x 25-ft and features an insulation R-value of 4.2. Check your local building codes prior to installation.