This is an efficient heat duct made from a durable urethane-coated polyester material that is resistant to water, mold, mildew and fire. It has a partial silicone liner that provides advanced 500 Degrees F heat protection at entry. For horizontal use only, this duct measures 25 feet in length and 16 inches in diameter, and comes with integrated compression straps to help minimize storage space. It also has pin-lock, belted cuff collars.