It is well known that choosing the correct size of flange (breastshield) is important to achieve comfortable breastmilk pumping. While Ameda provide CustomFit flanges, some of the sizes are achieved using inserts which are not easy to use, and tend to leak air easily. Maymom Breastshield for Ameda Breast Pumps is one-piece design to achieve the size you want. Its one-piece design makes it easy to clean and also means there are fewer parts to store with less chance of losing suction. BPA-free and steam safe for sterilization, this Maymom Breastshield also complies with US FDA standards for your reassurance!