Speedi-Products FD-12R8 08 8-Inch Diameter by 12-Feet Length R8 Insulated Flexible Duct with Metalized Jacket R8 fiberglass insulation for improved energy efficiency & noise absorption Polyethylene sleeve separates airflow from insulation Cut to length for each specific application Can be used in Supply, Return and standard exhaust applications Ideal for duct systems within the conditioned space