Grout Aide Marker is made with an antibacterial formula that covers and restores your grout to its original white beauty. Works just like a marker to paint over stained grout. Makes old grout look better than new instantly! Penetrates deep down, permanently seals. Restore grout to a bright and clean condition with Grout-Aide. The fast drying markers quickly revitalize old, discolored grout and cover stubborn grout stains instantly. One marker covers about 175 feet of average grout lines.