Alessandra B Adhesive Nipple Covers are made of medical grade silicone which is safe for sensitive skin. The Nipple covers can be used many times, and cleaning is easy with warm water and soft soap. They are packed in a Black Magnet Box convenient for travel. While other suppliers offer their nipple covers only with one size of diameter of 3.2" which fits A,B,C cups, Alessandra B offers two versions of nipple covers, one size of diameter of 3.2" to fit A,B,C cups, and another size of diameter of 4.0" to fit D,D,DD and cups.