Environmentally friendly. Cleans toilets for three months. Easily installed in less than five minutes; fits most two-piece toilets. Repels stains with every flush. Isolates cleaner from the tank water so tank parts aren't damaged by detergents or bleach used by other in-tank cleaners. Cleaner-treated water is injected only to the bowl where it's needed, so cleaner application is efficient. Carded.