Keep your cats using their litter box with the Ceva Animal Health D89410b Feliway Multicat Starter Kit. This unit plugs into a wall socket and releases calming pheromones to keep your cat stress-free. The diffuser plug-in should be replaced after 30 days and is designed to be used in homes with two or more cats. Each diffuser covers approximately 450 square feet depending on your individual circumstances and the number of cats that you own.