An acid based cleaner for removing hard water staining efflorescence from granite cemetery monuments, select stone masonry, as well as bathroom surfaces Additional Details ------------------------------ Bullet point: Versatile! Endurance Hardwater Stain Remover effectively removes hardwater staining and light rust from a variety of surfaces including granite, brick, block, grout, clay tile, glazed and vitreous tile. Endurance Hardwater Stain Remover will also clean porcelain tubs, sinks, toilets and shower heads. Please note that this product should not be used on limestone, marble or real travertine