Medela's Breast Milk Storage Bags enables you to store extra breast milk in the fridge or freezer, so your baby won't need supplementary food or liquids if their demand changes. The ready-to-be-used Breast Milk Storage Bags make storing, transporting and warming of your breast milk, convenient and hygienic. The bags have a freezer-proof, double zipper protection to prevent leaking and are more space-saving than using bottles. The flat shape of the bags ensures milk thaws quickly and the durable material is safe for freezer storage.