ConvaTec SUR-FIT Natura - Disposable Convex Inserts are designed to be used with recessed, retracted or flush stomas. The Convex insert provides extra protection by snapping into the coupling ring of a SUR-FIT Natura Durahesive or Stomahesive skin barrier. To determine which size is needed simply select an insert that is at least 1/4" larger than the maximum diameter of the stoma. Look no further than ConvaTec for reliable, quality ostomy supplies and accessories.