Specifically designed for the Fluval Betta Aquarium Kit (6 US Gal / 22.7 L model), the Betta Poly-Carb Cartridge offers effective 2-in-1 mechanical and chemical filtration for clean and clear water. Mechanical and chemical filter media Carbon-impregnated polyester cartridge Effectively traps fine debris and contaminants Removes harmful toxins, discolorations and odors For best results, replace every 2-4 weeks Convenient 4-pack format Size: 4-Pack