This is the second CatGenie I've owned...the first one didn't have "Cat Activation", which I think is a MUST!!! (who wants to smell cat poop for several hours?). The two Maine Coons that I rescued are just too big to fit under the dome (one of them nearly stands up straight when going #2). I still use the additional high sides that you can purchase, but the dome is only used when I'm cleaning the bathroom and don't want to drop something in the box or accidentally activate it. I'd recommend taking your cat's size and elimination posture into consideration before buying the dome.