Coretek flips and currency holders meet the highest standard in archival quality material available on the market today for coin storage. To meet this standard, Coretek uses a polyester film that is 100% uncoated, colorless, biaxially-oriented PET. That means no plastic, no additives or UV inhibitors, no surface coatings, no absorbents or other contaminants. Coretek is a truly archival product line and represents the best practices in archival materials for coin and currency holders. Item comes in packs of 50.