Drinkwell's 360 Replacement Filters are designed specifically to fit the Drinkwell 360 Fountains to keep water fresh and clean. For easy insertion and removal, the cylinder shaped filter features a pull-tab on the top. The filter should be replaced every 2 - 4 weeks. The filter is made with a duo density polyester pad that captures debris and unwanted dirt, additionally, the filter contains granulated carbon for extended filtration.