Marineland Rite-Size Replacement Cartridge Size Z - 12 Total (4 Packs with 3 per Pack) 12 Total Filters (4 Packs with 3 per Pack) Marineland Rite-Size Replacement Cartridge Size Z There's a Rite-Size cartridge for every Penguin, Emperor, and millennium power filter Is designed specifically for horizontal placement in our extensive selection of Eclipse systems Delivers crystal clear, crystal clean water