Pre-filled with premium blue crystal cat litter, the disposable PetSafe ScoopFree Premium Blue Crystal Cat Litter Tray works with PetSafe ScoopFree Self-Cleaning Cat Litter Boxes. Just load the tray in the litter box and leave it for weeks with no scooping, cleaning or refilling! The crystal litter absorbs urine and dries solid waste quickly to remove odors. With the completely disposable tray and covered waste trap, you never see or touch smelly waste! Every few weeks simply replace the litter tray and your ScoopFree Self-Cleaning Cat Litter Box is just like new.