Marineland Rite Size Cartridge A meet the absolute highest standards of water purification. Performance and operational ease. This preassembled cartridge slides easily into place. Providing superior mechanical and chemical filtration and making replacement fast, dry and effortless. Inside the cartridge, a patented ribbed backing ensures even distribution of activated carbon to deliver maximum water to carbon contact. The cartridge mechanically filters water through a pad of double thick poly fiber. Debris and waste particles are trapped and water is chemically filtered through Marineland' s Black Diamond premium activated carbon. Fits Penguin 100B, Bio-wheel Mini and Penguin 99B power filter. Comes in a single pack.