A retaining ring includes a generally annular body having an inner surface to constrain a substrate, an outer surface, and a bottom surface. The bottom surface has a plurality of channels extending from the outer surface to the inner surface and a plurality of islands separated by the channels and providing a contact area to contact a polishing pad. Each channel includes a recessed region adjacent the outer surface such that the channel is deeper in the recessed region than in a remainder of the channel. The recessed region and the remainder of the channel each have substantially uniform depth.