Designed by cat-loving MIT-trained engineers, the PetSafe ScoopFree Self-Cleaning Litter Box features breakthrough technology to provide matchless odor control and hands-off convenience. The self-cleaning system works by automatically raking waste into a covered compartment every 20 minutes after your cat uses the litter box. Sensors detect your catas movement and reset the 20 minute timer. The ScoopFree system comes pre-loaded with an innovative crystal litter tray that is 5 times for effective at reducing odor compared to clay or clumping litters. Just one ScoopFree Crystals Litter Tray lasts as long as 30 lbs. of the leading clay litter. Simply replace the ScoopFree Blue Crystals Litter Tray about once a month for each cat. No more scooping each day! Features: Leave it alone for up to 30 days* Disposable tray pre-filled with ScoopFree Crystals Crystal litter locks away odors No scooping, cleaning or re-filling litter Automatically rakes solids into covered trap Convenient, reliable, quiet and hands-off PetSafe ScoopFree Crystals Litter Tray refills are sold separately Environment Type: Litter Box Species: Cats Package Dimensions: 14" x 14". The exterior dimensions of ScoopFree are 27 3/8" x 19" x 7". The height is 16 3/4" with the optional hood installed. Caution: Never add litter to your ScoopFree box or use another type or brand of litter. The PetSafe ScoopFree Crystals Litter Tray is formulated especially for the ScoopFree Self-Cleaning Litter Box. How it Works: Open your pre-packaged ScoopFree Blue Crystals Litter Tray. Slide tray into automatic litter box. Store tray cover under litter tray for later disposal. There's nothing to fill, empty or clean for up to 30 days* After your cat uses the PetSafe ScoopFree box, the ScoopFree crystal litter immediately starts to absorb liquid waste and dry out solid waste. 20 minutes after your cat leaves the b