PET/ aluminum foil /RCPE, the outer layer of PET, can print patterns and has certain barrier properties. Aluminum foil enhances its barrier property, while RCPE inner layer can withstand high temperature cooking at 120 degrees, can be heat sealed, and also has certain barrier property. You can buy a sauce bag to see. Almost all of them are multi-layered, which is just one of the better ones, and the cost will not be too high.