Welcome to APi Distribution!
Ideal Tape's 491 is a pressure sensitive tape manufactured with the FSK Foil, skrim and kraft combined with a pressure sensitive adhesive and release liner.
491 is used for sealing cold and dual temperature duct seams and joints where FSK is the basic insulation facing. The pre-cut 491D discs are applied over washers and cupped pin heads. They can also be used to cover any accidental punctures in the insulation facing. The discs provide an excellent vapor seal when applied to clean, dry surfaces.