Scrub away stubborn stains on pool and spa tile, grout, and concrete using this PRO SIZE pumice stone. This cleaning stone is made from 100% PURE PUMICE, is chemically neutral and wont harm your pool, hot tub or spa water. Simply wet area before cleaning and gently rub stain away from pool walls, floors, pool stairs or grout. Whether you are cleaning the grout in your pool or bathroom or algae stains from concrete, this stone is tough and always up for a good scrubbing challenge. ALWAYS TEST a small area BEFORE using to ensure it will not scuff or scratch. Please, never use on over-glazed ceramic or other soft material like fiberglass, wood, polished metal, glass, or plastic surfaces. Stone measures 6 W x 2.75 D x 2.75 H.