The Dr. Brown's Natural Flow Microwave Steam Sterilizer Bags sterilizes parts from Dr. Brown's baby bottles, eliminating 99.9% of most household bacteria and germs. They are designed to fit all Dr. Brown's baby bottle parts, and they are perfect for steam cleaning while on?the?go or while traveling. Five sterilizer bags come to a pack, and each bag is reusable ? up to 20 times. This offers moms 100 uses per retail pack.