AquaClear Activated Carbon Filter Insert contains 100% premium research grade carbon. Premium research grade carbon provides large amounts of surface area for adsorption of undesirable impurities. Use of the activated carbon filter insert will remove unwanted odors, discoloration and impurities resulting in a crystal clear aquarium. Designed for use with AquaClear 20 (formerly AquaClear Mini) Power Filters. Shipping weight: 1/2 lb.