1 Device. Improved Design! Hides in tank! Cleans with every flush! Lasts up to 3 months. 100% Tough! Satisfaction guaranteed. Easy to install! Constant Cleaning Action Prevents: Ring around the toilet. Rust. Hard water. Quick to install! Kaboom Scrub Free! is a revolutionary automatic toilet cleaning system that easily attaches out of sight within your toilet tank. It injects a powerful cleaning formula into the toilet bowl with every flush, keeping it clean, even under the rim, for up to 3 months! Won't harm tank parts (like drop-in solids or pucks). Safe for septic systems.