This is the most annoying machine. If you overfill, even a tiny bit, the rake will go back and forth until you want to throw it out the window. If you put too little litter, then the bottom is filled with urine and sticks to the rake. They really need to fix this problem. They need to make it so that you can put enough litter in to actually fill the box and keep urine off the bottom and for the rake to not be so incredibly sensitive. Until they come up with a better one, for us this is just going to be an overpriced litter box.