AquaClear Activated Carbon Filter Insert improves water clarity in fresh and saltwater aquariums. Exclusively designed for the AquaClear Power Filter, it provides superior adsorption qualities which eliminate odors, discoloration and impurities. Available in the following sizes: Filter Insert for AquaClear 20 single or 3 pack Filter Insert for AquaClear 30 single or 3 pack Filter Insert for AquaClear 50 single or 3 pack Filter Insert for AquaClear 70 single or 3 pack Filter Insert for AquaClear 110 single