this kind of cutting sand disc mainly use in air tools or power ... tools, for grinding metak. the material is aluminum oxide. Sand disc Specifications1) Sizes: 4", 4.5", 5", 6", 7 ... zirconia oxide3) Usage: grinding weld seam, removing burr, sanding floor or furniture, polishing stainless steel fork or spoon. ... stable performanceOne hole depressed center aluminum oxide fiber disc for metal sanding disc