Specially developed to keep pool tile, grout, vinyl liners, and fiberglass looking their stain-free best. Its fast-acting, multi-acid formulation starts working on contact, providing immediate visible cleaning action. The tile plus stuff has gel-like properties that adhere to the surface of tile, grout, vinyl liners, and fiberglass for maximum cleaning of scale, metal stains (including rust) , oils, and cosmetics. This product will not etch tile or grout when used as directed, and is compatible with all pool sanitizer systems.