The ScoopFree litter tray is the reason you can leave ScoopFree self-cleaning litter boxes alone for weeks at a time. The tray is completely disposable for hands-off convenience. You don't have to see, touch or smell messy waste. It is pre-filled with Premium Blue Crystal litter, which has been proven to provide unbeatable odor control. Simply replace the disposable tray every few weeks, and your ScoopFree litter box is just like new. Each crystal litter tray will last up to 30 days, depending on number of cats. The litter tray is not intended for kittens under 6 months old.