Nashua Tapes Products 327 PREMIUM FOIL TAPE - BUTYL RUBBER Heavy-duty 17 mil printed aluminum foil tape with butyl rubber. Applications Duct joint sealing for low, medium and high pressure HVAC systems. Sheet metal repairs. A general purpose repair tape for aluminum siding, storage buildings, flashing, gutters, awnings and other applications. Features & Benefits Very aggressive adhesive stays pliable and resists releasing. Instant air and water tight bond to sheet metal, duct wrap barriers, duct board and flexduct. High tensile strength. Paintable. Clean, 0n-hazardous and easy to use alternative for mastics.