Marineland Canister Filter Ceramic Rings Rite-Size S, Rite-Size T, 420-Count Total (3 Packs with 140 Rings per Pack) 420-Count Total (3 Packs with 140 Rings per Pack) Provide Porous Surface Area for Support of Biological Filtration Fits all C-Series Canister Filters Do not clean with soaps or abrasives and never rinse with unconditioned tap water