The AVENT Isis Comfort Breast Shells are ultra comfortable breast shells that are worn inside your bra to protect your nipples from chafing and to collect excess breast milk. The Isis Comfort Breast Shells help to protect sore nipples. The ventilated shells with the holes protect sore or cracked nipples to help them heal more quickly. Their gentle pressure helps relieve engorgement and the holes allow air to circulate. And the breast milk collection shells with no holes collect excess breast milk when feeding or using a breast. pump.