The Drinkwell Platinum Filters feature six compartments of charcoal! This evenly distributes the charcoal for a longer lasting， deeper water filtration. More charcoal is added to each compartment to maximize water filtration. This filter will work with ANY Drinkwell Fountain (except the Drinkwell 360) and should be changed every 2-4 weeks to maintain water freshness. There are three filters per package.