2000 Flushes Blue + Bleach Anti-Bacterial System is a 2-part system that keeps your toilet clean and fresh for up to 4 months. It includes a blue block to clean and freshen, and an anti-bacterial bleach tablet that kills 99.9% of bacteria. Simply drop it in the toilet tank, and it will continuously clean and deodorize your toilet with every flush, helping to prevent stains and keep your bathroom smelling fresh.