The theory behind this litterbox is genius, but it doesn't work as advertised.  My cat urinates in the back corner, and the rake never could get it.  It would scrape off part of the clump, which would get stuck to the rake, but it would leave the majority of it in the corner.  The clumps would stick the bottom of the pan, and it was a real pain to clean them off.  I had to scoop this litterbox and clean the rake off 4 times in the two days I used it, which is twice as much as I scoop my regular litterbox in a whole week!  Don't waste your money.