Sparkling Water Made Simple - Dual-action aquarium filter cartridge designed for Cascade 300 GPH hang-on filters. Activated carbon removes discoloration and odors while the poly-fiber layer traps particles - keeping your fish tank water clean and clear. Healthier Habitat for Fish - These filter cartridges provide efficient filtration for both freshwater and marine aquariums, helping maintain a balanced and stable aquatic environment. Easy Upkeep, Every Time - Each filter cartridge typically lasts up to 6-12 weeks depending on tank conditions. The preassembled design allows quick, clean replacement with no messy setup-simply slide the cartridge into the filter compartment for effective filtration. Compact Fit, Consistent Flow - Perfectly measured to fit Cascade 300 model (CPF5), these black or blue filter cartridges prevent debris bypass. Dimensions: approximately ‎10 x 3 x 7 inches. Sold in a convenient 3-pack for easy replacement. Penn-Plax Legacy - With over 60 years of innovation, Penn-Plax creates expertly crafted, dependable pet products designed to enrich habitats, inspire creativity, and promote the health and happiness of pets everywhere