Our Flap Disc Sanders are manufactured using premium aluminum oxide grain on a heavy cloth backing. The abrasive grain material is superior due to its uniform particle size, aggressive cut and premium blend of ingredients. Flap discs are great accessories for working on wood applications and similar to the ones designed for use on metal. In order to avoid deep scratches, start with a heavy (low number) grit and work your way up to the lighter grits (100+) for a final finish. For sanding, work your way through 120, 180, 240, 320 and higher grit sizes to achieve a furniture-grade surface