Philips Avent Sealing Discs transforms the Avent bottles into storage units. You can feed with the same bottle and then store it away for later use. The discs are safe for the freezer, and the material is writable so that you can record the storage date. Philips Avent sealing discs are made from two BPA free materials - Thermoplastic elastomer (TPE) and Polypropylene (PP)