Many HVAC contractors use cloth duct tape to seal between duct sections, but film tape is also an option. Designed for sealing Class 1 Flex duct, Shurtape’s DC 181 film tape is hand-tearable, UL 181B-FX listed, and has a polypropylene face film and water-based acrylic adhesive. Available in 2- and 3-inch widths for about $9.50 and $14.20 per roll. Shurtape, 888.442.8273, shurtape.com