Continuously cleans. Non-stop freshness. Hygienic clean (Not a disinfectant or sanitizer). Up to 16 weeks (Each cube lasts up to 4 weeks). Safe For: Septic tanks. Toilet components. Cleans & freshens with every flush. Helps fight toiler ring, hard water & limescale stains. Safe for toilet components. Easy to use. Safe for toilet components and septic tanks.