Aqueon Replacement Filter Cartridges are made with a patented dual-sided dense-floss contain over 25% more activated carbon than the leading brands. These unique cartridges were designed to ensure even distribution of carbon throughout the cartridge. This Large cartridge is for use with Aqueon filters. To use, simply rinse under cold water and install. Aqueon Replacement Cartridges are available in: X-Small, Small, Medium.