The Petmate Replendish Charcoal Replacement Filters are specifically designed to fit Replendish systems. The unique external polymer material captures sediment and debris. The internal charcoal elements control chlorine levels and prevent odor. These parts work together to eliminate impurities and provide pets with healthy and clean water they enjoy. The replacement filters last up to eight weeks for a longer-lasting filtering system. Pet parents can easily secure a replacement filter into the Replendish with the included filter strap. The packs come in 3 or 6 counts. For easy use, match your Replendish system with the appropriate filter product number, remove the outer plastic covering, and rinse the filter under cold water until it runs clear before placement.