I got the Scoopfree Premium Blue Crystal's Litter Trays 3 pack for the Scoopfree Selfcleaning Litter Box. We have 2 cats and this litter worked well. With 2 cats it says to change after 15 days depending on your cats. I changed between 10 to 12 days. It it a great feeling not to have to do the litter box all the time. I am amazed that it did not smell. The odor control is great! I would buy this product again.