I was a little skeptical about a self cleaning litter box mostly because the cat waste stays in the box. But this crystal litter is amazing at eliminating that urine odor. This box operates by simply raking the solid waste into closed compartment, the crystal litter is non clumping so the urine stays but it doesn't smell for a week. I have three cats using it so it doesn't last as long as it would with one. I'm giving this litter box four stars just because I still end up cleaning the solid waste out of the compartment because it is super small. And I don't like that it doesn't come with a permanent litter tray, instead you have to buy one or buy disposable ones every time you change the litter. Overall I am happy and impressed with this litter box.