Medela breast milk bottles have been designed for the safe, long-term storage of breast milk. You can pump breast milk directly into the baby bottles and store it. You can also feed your baby using the same bottle. The bottles are made from a safe plastic designed to retain the breast milk's beneficial properties and are ideal for the safe storage of breast milk in the refrigerator or freezer. The colorful ounce and millimetre markers make it easy to measure the exact amount of milk you have expressed. The bottles also feature screw-on lids so that they do not leak when they are stored in the fridge or freezer, or transported when you are travelling. They are also shatterproof, BPA-free and Pthalate-free.