Our #1 selling litter "” ultra has superior odor control and is perfect for multi-cat families and those cat owners with sifting or mechanical litter boxes. Dr. Elsey's ultra litter is a unique formulation that combines the heavy non-tracking granules of the classic litter with a medium grain clay. The result is an excellent clumping litter that prevents moisture from reaching the bottom of the tray while providing a clump that will not break down. As seen on buzzfeed and in the new york times' wirecutter.