Marineland Rite-Size E Emperor Cartridges are designed to meet the highest possible standards in aquarium water purification and performance. These pre-assembled replacement cartridges fit Marineland Emperor 280 or 400 filters and are designed for fast and effortless replacement. Each E Emperor cartridge features a pad of double-thick polyfiber that mechanically filters water for the cleanest and most pure water. Additionally, the water is chemically filtered through Marineland's Black Diamond Premium Activated Carbon that ensures the most superior chemical filtration. It also features a patented ribbed, crystal backing for even distribution of activated carbon, leaving only crystal-clear water.