Bloo In Cistern Twin Blocks Citrus Zest provides a hygienically clean and fresh toilet with clear water with every flush. Its strong foaming action prevents dirt, and its super cleaning agents are designed to prevent limescale, keeping your toilet hygienically clean between deep cleans. This in-cistern block produces clear and foamy water every time you flush. Each pack lasts up to 8 weeks for an enjoyable toilet experience. Simply place the block in your toilet cistern to clean from the cistern to the bowl with every flush. It cleans and foams with every flush and prevents limescale build-up.