Scoopfree Premium Blue Crystals Replacement Litter Tray for the ScoopFree Original Litter Box.

Tray Replacement chart:

Number of Cats 1 - 20-30 days
Number of Cats 2 - 10-15 days
Number of Cats 3+ - 7-10 days

Scoopfree Litter Box - Watch it in action!