The beauty of using the Air-Tite holder with the ring is that it can be used for different diameters or irregular shaped items. I believe that the "foam" ring is made of an inert material that will not tarnish ones coins or tokens. Some very expensive rare coins are housed in Air-Tites by many of the nation's leading coin dealers and museums. I don't think that they would take a big risk on a product that has not been proved safe.