Ceramic resin fiber grinding discs are best for cool, rapid stock removal on all heat sensitive metals including stainless steel and high nickel alloys. Prevents discoloration. Discs have center hole for use on electric or air right angle disc sanders. Ceramic grains are tougher than aluminum oxide, and are self-sharpening. It is formed in a process where alumina gel is dried and then crushed. These engineered crystals fracture and refracture at fine levels, to form a smooth, self-sharpening abrasive material. Ceramic aluminum oxide is most commonly used for medium-to-high material removal on metals.