First things first, BUY THE ETRA RINGS! you have to be more stubborn than your cats & absolutely determined for them to succeed. You also have to remove EVERY OTHER litter tray & make sure the rings are kept immaculately clean at all times. If you cannot do this for any reason, you are wasting your time, money & upsetting your cats. I started with my Burmese girl 11 years ago. She was 6 months & is a very tiny cat. She hasn't used a tray since - Imagine the money I have saved!!!!