1-piece convex ostomy pouches have a wafer attached to the bag that contours inward toward the abdomen. This puts light pressure on the abdomen and causes the stoma to protrude out farther than it does naturally. A convex ostomy bag ideal for people with recessed or flush stomas. We carry pouches with varying degrees of convexity depending on how far your stoma is recessed. If you have a flus hor recessed stoma and use a flat ostomy wafer, output might not drain into the bag properly. It can leak between the wafer and your skin and cause skin irritation.