The new DeWalt Type 27 Depressed Center wheels are formulated with aluminum oxide for grinding harder metals such as stainless steel, super alloys, and othere high tensile alloys. This formulation provides aggressive material removal and long life on ferrous metals (steel, iron welds, edge grinding). DeWalt utilizes an industry recognized color coding and identification system to help users identify the right bonded abrasive wheel for their application. theree are also several key identifiers to look for on a DeWalt wheel; RPM, wheel size, thickness, and arbor size to ensure the correct product is used.