Cutting wheels, or cut-off wheels, are abrasive wheels designed for clean cuts through metals. Cutting wheels come in two main types; Type 1 and Type 27. Type 1 cut-off wheels are flat for the most cutting depth, while Type 27 cutting wheels have depressed centers to allow better visibility while cutting. The grain that makes up a cutting wheel's composition determines its cutting speed and life span. Aluminum Oxide is the most common abrasive grit and delivers excellent value.