My cat has the unique talent of being able to pee on the roof of his box. You have to see it to believe it, but it's his box and he gets to do his thing however he wants! No filter will eliminate those odors, but the filter prevents him from peeing through the slats in the lid. The filters can be rinsed with water between changes. To eliminate odors from my talented kitty's ability to pee on the roof I spray the filter wth Simple Solution as needed to keep it odor free.

Pros: easy to change

Cons: none

This product is probably better for one cat but not for four cats.

Pros: Scent is good

Cons: Not good for multipule cats