Effortlessly erases stains with only water. Blue urethane foam sponge holds water to keep pad moist, can be used to wipe after use, and keeps the pad intact over its useful life. Pad will not scratch glass, ceramic tile, fiberglass, porcelain, Formica ®, metal, Corian ®, marble, stainless steel, plastic, vinyl, and most wall coatings. Ideal on crayon and marker.