Convert your Dula Wide Neck Breastmilk Storage Bottle Avent Natural and Classic Plus Spectra Bottles Maymom Screw Rings Pigeon Wide Neck Bottles Mam Bottles and all other wide neck bottles to storage container to feed, express and store. This is also compatible with Dula Wide Neck Breastmilk Storage Bottle if in case you lost the included sealing disc. Dula Silicone Disc is made from food grade liquid silicone and its BPA Free