CatGenie SaniSolution 60-Original CartridgeThe cat-safe SaniSolution decontaminates the Granules and cat box of germs and odors. We recommend at least 1 cleaning per day per cat. Cartridge is biodegradable and recyclable. One cartridge lasts approximately 2 months for one cat and 1 month for two cats etc. Always keep an extra Cartridge. The CatGenie can't run on empty. Can only be used with CatGenie 60-Original Cat Litter Box.