When properly installed with an induction sealer, the cap's heat sealable liner forms an airtight innerseal that protects contents against moisture and oxygen, and provides a tamper-evident seal. Liner is a paper-backed aluminum foil coated liner with a clear, heat sealable coating that is laminated to a polystyrene foam. Can be used on Polyethylene, PET, PVC, Polystyrene and Polypropylene. Also, may be used on glass treated for proper adhesion. Not suitable for products containing oil.