Penn Plax is a name that stands for Quality, Innovation and Integrity, In the Pet Industry for over 50 years, Experience a great line of Pet Products in all categories!, Penn-Plax is committed to creating and manufacturing innovative pet products for first-time pet owners and serious hobbyists alike, Penn Plax Cascade 300 Filter Cartridges contains 4, 5 ounces of research-grade activated carbon, The internal rib structure evenly distributes carbon throughout the cartridge for the most effective filtration, Change monthly for maximum filtration, Category: Aquarium Supplies/Maintenance, Sub Category: Filter Cartridges, Cubes: 0, 0033, Weight: 1, 8900, SKU: PPPHM256