REPLACEMENT CARBON FILTER: Keeps aquarium water crystal clear – removes odors and discoloration. CATCHES DEBRIS: Dense, dual-sided mesh filters debris and fish waste. FITS TETRA WHISPER WATER FILTERS: Color coded to make it simple to remember which replacement cartridge size to purchase. CONVENIENT: Replacement filter cartridges are fully assembled and ready to use. USAGE: Change monthly or sooner if needed. Conveniently Assembled and Ready-to-Use Like the unassembled, the-Packages are color-coded, making it easier than ever to remember which size to purchase Easy to Assemble, Easy to Replace Please read all label information on delivery