The Top Fin Silenstream Large PF-L Filter Cartridges come in a convenient 9-count package, designed for use in 30-gallon tanks. These filter cartridges are specifically for freshwater tanks and provide efficient filtration for optimal water clarity. With the TOP FIN Silenstream model offering great functionality, these cartridges are compatible with many Top Fin filtration systems, providing a reliable solution for maintaining clean and healthy water in your aquarium.