Each Marineland cartridge is designed to meet the highest standards or water purification performance and operational ease. They slide easily into place, providing superior mechanical and chemical filtration, and making replacement fast, dry, and effortless. Cartridges mechanically filters water through a double thick poly-fiber. Debris and waste particles are trapped, and water is chemically filtered through Marineland Black Diamond Premium Activated Carbon. The result - crystal clear, crystal clean water!