Tetrafauna ReptoFilter Cartridge 3-Pack is filled with Ultra Activated carbon, the ready to use disposable cartridge removes waste particles, odors and discoloration. Fully assembled and ready to use Keep water crystal clear Remove odor and discoloration ReptoFilter Reptile Cartridges are tough on debris but easy on you. Ultra-activated carbon absorbs odors and discoloration while dense, dual sided mesh catches debris and waste, leaving your pets water clear, clean and healthy. Replace filter cartridge every 28 days for clean, healthy water.Specifications:Medium: Fits 90 GPH/10i Filter, Decorative ReptoFilter & ViquariumLarge: Fits 125 GPH Filter