I used tofu at first, as I read this in one of the reviews. My cats only ever used crystals, they didn't touch the kitty machine for a week. I left one of their old ones out during the transition. I then changed to clumping clay, my elder cat started peeing in there as it's easy access for him. I can confirm I am so happy with the poop going straight into the garbage bag, there has been no odour so I'm impressed.
I clean the bin regularly everything is easy to clean, I'm very happy. My youngest...