[Compatible] Filter compatible with the Drinkwell animal waterer. removes bad stains and odors [Economical] 12 pieces to replace the Drinkwell carbon filter element. [Residual hair and debris] Dual density polyester pad can trap hair and debris to get fresh and clean water. [Replacement] 2-4 weeks Although our fountain filter can be used for a long time, in order to provide the best protection for our animals, we recommend replacing it every 2 to 4 weeks.