ScoopFree® is the self-cleaning litter box you can leave alone for weeks at a time. It is the only self-cleaning cat litter box that uses disposable litter trays to provide hands-off convenience and unbeatable odour control. The rake automatically sweeps waste into the covered compartment 20 minutes after your cat uses the litter box. The Ultra comes with Adjustable Rake Delay allowing you to choose if the automatic rake sweeps waste 5, 10 or 20 minutes after your cats use the litter box.