UL181A & B New & Improved - Cold Weather, Premium Grade, Printed Foil Tape (with Liner) For Hvac Applications. Recommended For Use On UL Listed Fiberglass Duct Board In Accordance with Manufacturer's Installation Instructions. Ideal For Permanent Flexible Seals. Meets UL181 A-P Standard For Use As A Closure Material On Fiberglass Duct Systems and UL181 B-FX Standards For Use On Flexible Air Ducts and Closures.