ConvaTec SUR-FIT® Natura® Two-Piece Disposable Convex Insert 1-1/2" Inner Diameter Opening, For Use with 2-1/4" SUR-FIT® Natura® Skin Barriers SUR-FIT® Natura® Disposable Convex Inserts are designed to snap into the flange/ring adding convexity to the standard skin barrier/wafer for improved management of retracted stomas.