3311 is ideal for sealing joints and seams against moisture and vapor on foil jacketing insulation. It can also be used in general maintenance and automotive repair.Scotch Foil Tape 3311 10A, 2.0 in x 10 yd (50.8 mm x 9,1 m). Specifically designed to help maintain duct work integrity and optimize HVAC performance. conformable tape with silicone treated liner that unwinds easily to minimize errors and wasted tape . It is flexible and easy to apply in tight spaces, making it the ideal tape for duct repairs. The soft aluminum foil also conforms to irregular surfaces and provides a reliable vapor barrier.