Marineland products are designed with both performance and style in mind. We push precision and power beyond the expected and listened to our loyal customers to make our products even better. We do this because at the heart of our innovative spirit is a desire to help hobbyists everywhere do more, create more and, most of all, enjoy more. So whatever you¥ passionate about - freshwater or saltwater, big or small, beauty or science - make your aquarium your own. Marineland Penguin Power Filter Cartridges are designed to meet the standards of water purification, performance and operational ease. Each replacement cartridge is pre-assembled and slides easily into place, providing 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 Black Diamond Premium Activated Carbon. Inside the cartridge, a ribbed backing ensures even distribution of activated carbon to deliver maximum water-to-carbon contact. The result is sparkling clean water. The Marineland Penguin Power Filter Cartridges feature convenient, color-coded Rite-Size packaging to make it simple to choose the right replacement cartridge. These filter cartridges fit Penguin PRO Power Filters 275 and 375, as well as original Penguin Power Filters 200 and 350. For best results, replace monthly.