Aluminum Oxide is a general purpose mineral that works well is most applications. Aluminum Zirconia is sharper than aluminum oxide providing a faster cut rate when speed is important. Ceramic minerals are very hard and provide a long lasting wheel life in high production applications. Ceramic A/O Blend is a great combination of performance and price. Cubitron II is 3M's precision shaped grain; it offers top of the line cut rate and abrasive life.