Each preassembled Penguin Filter Cartridge filters aquarium water through a double thick polyfiber pad which traps more dirt and debris, faster. The filter cartridge is packed with super-efficient pure Magnum Activated Carbon, it keeps working long after most carbons stop. It's better than a bag: just shake and rinse. The patented ribbed backing evenly distributes carbon for maximum water to carbon contact. No bypass, no tea bag effect, just crystal clear, crystal clean aquarium water. Each Penguin Filter replacement cartridge includes a foam pad and carbon for superior mechanical and chemical filtration. The easiest way to superior aquarium filtration.