Lansinoh's breast milk storage bags are super strong for storing, protecting, freezing, and thawing precious breastmilk. Our breast milk storing bags are pre-sterilized with a double zipper seal and double side seam to help prevent leaks while freezing and thawing mom's liquid gold for baby. Pump directly into our breast milk collecting bags with Lansinoh pumps or by using our pump adapter with most major pump brands. Bags hold up to 6 ounces of breastmilk and have an easy write label for better tracking. Each bag can be stored upright in the fridge or laid flat in the freezer for extra flexibility.