Grit Textures: Each Cratex size and shape is made in four standard grit textures or compositions which differ in accordance with the mesh size of the abrasive grain used. Coarse (Green) Medium (Dark Brown) Fine (Reddish Brown) and Extra Fine (Grey Green). Cratex Blocks and Sticks are excellent hand tools for cleaning and polishing metal surfaces, for breaking edges, smoothing away high spots, removing rust, heat marks, tarnish and stains. Designed for either manual or mechanical operation, they can be mounted in tool holding fixtures, chucks, or cradles. Use them for polishing shafts...damaskeening...cleaning and dressing diamond wheels...polishing rotating cylindrical parts, cleaning calibrations and reference points, and for removing feather edges and touching up cutting tools, dies, chisels and other sharp edged tools.