Marineland Rite-Size B Filter Cartridge for Penguin Bio-Wheel 125 & 150 Power Filters. Pre-assembled Penguin filter cartridges slides easily into place, providing superior mechanical and chemical filtration and making replacement fast, dry, and effortless. 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. For best results, change every 2-4 weeks.