Nashua 324A Cold Weather foil tape is UL code approved for sealing Class 1 rigid (181 Amp-P) or Class 1 flexible (181B-FX) duct joints and connections. With a heavy-duty foil backing that is printed for easy inspection and an aggressive acrylic adhesive Nashua 324 Amp is the ideal choice for heating, ventilation and air conditioning installations that require a code-approved product. Nashua Trusted Tapes get the job done right, the first time, every time.