The effervescent tablets for toilet bowl limescale do the hard work for you and are easy to use. Drop a tablet for 20 minutes and let the foaming action work deep within the U-bend, then simply flush! For tough cases, drop two tablets and leave overnight. In the morning, scrub lightly with the brush and flush. They remove limescale and limescale deposits, leave a fresh feeling in your toilet, and prevent the reappearance of blackness.