The Marineland Bio-Wheel Penguin Rite-Size C Filter Cartridge mechanically filters water through a pad of double thick poly-fiber, trapping debris and waste particles before the water is chemically filtered through Black Diamond Premium Activated Carbon. This pre-assembled cartridge is made with a patented ribbed backing to ensure even distribution of activated carbon and maximum water-to-carbon contact for crystal clear and clean water. The Bio-Wheel Penguin Rite-Size C Filter Cartridge slides easily into place, providing superior mechanical and chemical filtration and making replacement fast, dry and effortless.