Ceramic aluminum oxide is a self-sharpening grit that is harder, tougher, and lasts longer than aluminum oxide * Type 27 flat shape, for finishing * Full X-weight cotton cloth backing is stiffer, tougher, and thicker than a paper or film backing * Durable fiberglass backing plate helps absorb vibration and is consumed during use with no smearing * "Supersize" grinding aid provides a cooler cutting and faster cut rate