Keep your water clean and clear with a genuine Penn Plax filter cartridge to fit your Cascade 20 GPH Mini hang-on power filter model CPF6. Pack of 3. Activated carbon is great for freshwater aquarium filtration. It has the ability to remove odors; and water discoloration by trapping the pollutants in the pores of the carbon. The poly-fiber floss barrier screens out particulate matter and debris keeping the water clean; clear; and healthy. No assembly required keeping your hands clean. Easily install into interior compartment of your hang on filter. Suitable for freshwater and saltwater tanks. Perfectly measured to fit into the Cascade 20 filter tray without any gaps preventing debris and contaminants from passing through back into the water.