Thanks for your input everyone. If it sounds too good to be true there has to be a catch somewhere. I have the rolling litter box and that's the one they favour. But it's the small model and they barely fit in now that they are a year old. The other two boxes are way bigger and roomier and new but they rarely use them. The problem with the rolling one is that the wet "cookies" stick to the bottom and when I roll they don't come out and have to be scraped out anyways. Doesn't matter if there is lots of litter cause they dig around like crazy in there and leave an uneven layer !!! Maybe the round Booda box !!