The Sand Bar Sanding Sponge is the ultimate flexible sanding device. It is perfect for just about any sanding job, whether you"re working on curved contoured surfaces or large flat areas, and can be used on fiberglass, wood, or metal. It has a resilient variegated virgin foam core surrounded with an aggressive Aluminum Oxide abrasive coating, can be used wet or dry, and is long lasting and washable. Medium/Fine grit.