Harpic Flushmatic toilet cleaner works from inside the cistern to release a dose of powerful detergent with every flush. Harpic Flushmatic Toilet Cistern Block is a toilet hygiene product for continuous cleaning without any mess. It is touch free and hygienic and dissolves completely when finished. A single block lasts up to a month depending upon individual usage. It is safe to be used with septic tanks and all other toilet cleaners.