The Drinkwell Premium Filters feature 6-compartments which evenly distribute the charcoal for a longer lasting, deeper water filtration. The filter features a duo-density polyester pad to catch large particles such as hair and debris and more charcoal is added to each compartment to maximize water filtration. Premium Filters come in a 3-Pack and should be replaced every 2-4 weeks. [*This is our Standard Size Filter that is compatible among all fountain models with the exception of the Drinkwell 360 Models.][**This filter features 6-compartments and comes in CAT ONLY Packaging, typically merchandised with the Drinkwell Platinum Model.]