The Coralife Bio Cube Filter Cartridges fit all sizes of the Bio Cube all inclusive aquarium systems. Keep your aquarium in tip-top shape for your finned friends with Coralife's Bio Cube Aquarium Filter Cartridge. This filter cartridge is designed to fit all Bio Cube all-inclusive aquarium systems, which include sizes 8, 14, 29 and HQI. It helps remove odors and discoloration to keep your freshwater aquarium clean and clear for your underwater companions. And each purchase comes with two filter cartridges, so you always have an extra one ready to go. Replace your cartridge as needed to help keep your aquarium clean and pristine!