3326 Foil Tape is recommended for use on UL listed rigid fiberglass air duct in accordance with the Duct Board Manufacturers installation instructions.Scotch Foil Tape 3326 is especially designed for use on UL listed flexible and rigid air ducts. Its specially formulated acrylic adhesive bonds quickly and holds even at 25oF. Its soft aluminum handles and applies easily but still provides strength for UL 181A and ULB FX compliance. The printed backing provides code compliance verification for building inspectors.