Each tray is pre-filled with premium blue crystal cat litter, the disposable PetSafe® ScoopFree® Original Crystal Cat Litter Tray works with PetSafe® ScoopFree® Self-Cleaning Cat Litter Boxes. Just load the tray in the cat litter box with no scooping, cleaning or refilling for weeks! The crystal cat 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 cat litter tray and your ScoopFree® Self-Cleaning Cat Litter Box is just like new. Your pet deserves the best. Trust PetSafe® to help keep your pet healthy, safe and happy.