With a concentrated formula, the automatic toilet bowl cleaner delivers continuous cleaning action for up to four months. It uses powerful chlorine to bleach away stains to keep your toilet bowl continuously sanitary, stain-free, and deodorized. 2000 Flushes Toilet Bleach freshens your bowl and keeps the water crystal-clear with every flush. The cleaner is not harmful to plumbing or septic tanks when used as directed.