 Poolstone designed to clean tile, grout, and concrete pool surfaces. Work seven times faster than tile scrubs and two times faster than pumice stones. Remove hard water, rust, and mineral stains more effectively and won't scratch your tile. Additionally it is good night and plaster safe. Poolstone is made from 98% recycled material while being pool and filters safe so no need to drain your pool to clean. And it's so safe you can even put your kids to work cleaning those pool tiles. Grillstone and poolstone are guaranteed to continue catching the attention of consumers looking for a fast and easy way to tackle tough cleaning jobs.