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. PetSafe brand is here to help you and your pet live happy together.