The ultrasoft Avent breast shells are worn inside your bra to protect your nipples from chafing and to collect excess breast milk. Ultra comfortable breast shellsprotect sore, cracked nipples and provide relief from engorgement during or between pumping and nursing. The ventilated inner shell, padded by a soft silicone cushion, gently presses on the areola, creating a slow trickle of milk. The outer shell prevents leaks, holding the milk until it can be collected or discarded. The silicone shells can be sterilized in any Avent sterilizer.