When it comes to breast shell flanges for expressing breastmilk, one size does certainly not fit all. At Ardo, we cannot stress enough how important it is to make sure you have the correct size breast shell for you, your nipples, and your breast pump for a productive milk flow. Use the Ardo Breast Shells for the perfect pump, every time. Our soft silicone nursing breast shells are made from premium-quality BPA free materials, the best for you and your baby. The breast shell is the funnel-shaped part of the breast pump, which sits against your breasts when you are expressing. It collects the milk as it is expressed and channels it into the storage bottle you are pumping into. Getting the perfect fit ensures you are comfortable whilst pumping and you are maximising the amount of milk you express. The best way to determine which size you need is to measure your nipple (excluding the areola),to the widest part,add 4mm to this, and this is the breast shell you should try in terms of the diameter - the circle on the breast shells where your nipple will enter.