The present invention relates to a convex shell (1) for use in a base plate of an ostomy appliance. The convex shell comprises an annular ring (5) defined by an outer edge (6) and an inner edge (7) defining a through-going hole (8). The annular ring has at least four transition sections (9, 10, 11, 12) extending transversely across the annular ring, dividing the annular ring into at least a first, second, third and fourth segment (15, 16, 17, 18).