Lansinoh Sorage milk bags are ideal for storing, freezing and protecting precious breastmilk. They come pre-sterilized with a double zipper seal to prevent leakage.Presterilized for safe storage plus BPA and BPS free. Designed to lay flat for fast freezing and thawing to protect precious breastmilk vitamins and nutrients.Bags store flat in freezer, take up less space.It has a write-on tab outside fill area, which eliminates potential puncture and ink contamination.