The flexible, snap on Adapters are interchangable with both guard sizes and  are equipped with  a central opening in various sizes to accommodate your appliance size.  The outer circumference of the Adapter is intended to rest on a skin barrier’s outer tape portion and not directly on bare skin, as shown below. The central opening surrounds the circular plastic ring of a pouch flange, or the weld connection of a one piece appliance and maintaining the stoma guard over the stoma for optimal  protection. The back side, snap on adapter is soft to the touch with an uneven surface that has a cushioning effect and allows blood flow beneath, reducing the itchiness associated with applied pressure to the skin barrier over an extended period of time.  So comfortable you'll forget you're wearing it!