Whitening Magic Tile Grout Coating Pen 0.25oz is water-based formula that protects over stained patches that are caused by everyday mold and dirt build up on grout tiles. It is built with antibacterial & antifungal formula. The product is safe to use. It is Water resistant and comes with a valve activated control ink flow. Users highly recommended this product for all types of wall & floor grout. Use this product to cover stains breathe life back into the tiled surfaces of your home. Simply draw lines and pen through the cracks to revive it.