BathStone environmentally friendly cleaning blocks provide powerful effective and safe cleaning for hard water soap scum rust mineral build-up mold and mildew while contributing to a healthy environment. BathStone is made from recycled materials and saves the equivalent of 1 glass bottle from being added to landfills per stone. Non-toxic chemical free cleaning. Safe for your whole family. Works great on a variety of bathroom surfaces. Won t hold bacteria or viruses like sponges scrubbers. Say goodbye to hard water stains mildew soap scum and other buildup. BathStone a superior porcelain cleaner.. Now with sponge top. One block is 4 L x 2 W x 2 H. We feel this is the best hard water stain remover on the planet.