HiTauing 12 Packs PF-L Carbon Cartridge for Top Fin Silenstream PF20, PF30, PF40 and PF75 Power FiltersStrong Compatibility: The specific size of our aquarium filter cartridge is 6 in L x 4. 5 in W. It is very suitable for Top Fin PF20, PF30, PF40 and PF75 Power Filters. With this aquarium filter cartridge, you can keep your fish tank water healthy every moment. It contains 12 pack aquarium filter cottons, which you can change every 2 4 weeks. Excellent Filtration Performance: The filter cotton is made of cotton and carbon and has 3 layer filtering