Abstract: Apparatus and methods of polishing substrates are disclosed. A retaining ring for a polishing apparatus includes an inner surface exposed to contact a peripheral edge of a substrate to be polished against a polishing surface, a bottom surface exposed to contact the polishing surface while the substrate is being polished, and a wear marker indicative of a preselected amount of wear of the bottom surface. The inner surface, bottom surface and wear marker may form part of a retaining ring used in chemical mechanical polishing operations. In one method, one or more substrates may be polished against a polishing surface using the retaining ring, and at least a portion of the retainer may be replaced when the bottom surface has been worn away by the preselected amount indicated by the wear marker.