I absolutely love these. I bought the large size for my giant cat (he's 20 pounds), and the small one for my smaller cat who is only 5 pounds. For the large one, there is no litter catcher inside - the litter catcher goes on the outside. For the small one, the litter catcher is on the inside right in front of the door. If you have cats bigger than 12-15 pounds, I'd get the larger size as the amount of litter box space is smaller in the small one. Overall they're adorable and I Love them. They're also easy to clean.