Hard to know if it's the right one by Gretcheypoo03/20/2013
I ordered these filters because the picture looked right. No measurements listed in the description. Had to get 6 packages to get my total order to qualify for free shipping. Had to open one to learn it's the wrong size. Can only return 5 because they won't take open packages. Have to pay return shipping. Customer serivce did not offer to help me get the right ones. I'll save you the guesswork. They measure 5.5 inches long by 3.25 wide.
beware! by deg03/16/2013
This filter does not fit the Drinkwell 360 fountain. The web page fails to mention this.
Useful product great price by MaryB from Florida10/22/2012
I've used these filters before and found them very good for keeping the water fountain clean. I have a multi cat household and they are very fussy about the cleanliness of their water. Found them supplied here at a great price, delivered direct to my door. Thanks!