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.