400 plus Grit (Gray Green) 3/8 inch x 1 inch x 6 inch. Cratex rubberized blocks are excellent devices for touching up cutting tools, cleaning and polishing metal surfaces and removing rust or stains. They do not require honing oil. Cratex is made with oil resistant chemical rubber, selected reinforcing agents and embedded with high quality silicon carbide abrasive particles. It has excellent physical and chemical stability and is produced under strict quality controls to ensure reliable performance.