Abstract: An ostomy appliance in which the coupling ring assembly that detachably joins the faceplate and pouch of the appliance takes the form of a pair of flexible plastic rings, each ring being generally C-shaped in radial cross-section and defining an axially-facing annular channel. One of the rings is nested within the channel of the other ring when the rings are coupled together, with the inner and outer rings having opposing surfaces that sealingly engage each other and together define at least one circumferentially-extending fluid-isolating reservoir.