The Aqua Culture Filter Cartridges Model L are specifically designed for aquariums with a tank capacity between 20-55 gallons. These cartridges are essential for maintaining clean and healthy water in your fish tank. With four of these these 3-packs for a total of 12 cartridges, you can keep your aquarium running smoothly for an extended period of time without needing to worry about running out of filter cartridges. Made by a trusted brand like Aqua Culture, these cartridges ensure that your fish will have a safe and thriving environment to live in.