Metabo® Depressed Center Wheel, Type 27 General Purpose Tough, series: Original Grinding®, 9 in dia, 1/4 in Thickness, 7/8 in, A24R Grit, Coarse Grade, Aluminum Oxide Abrasive, 6600 RPM Maximum, Resin/Resinoid Bond, Applicable Materials: Steel and Ferrous Metals. The Quality of Cutting and Grinding Wheels Depends on Several Factors - The Grain (Size, Shape and Quality) Determines How Aggressive a Wheel Is. The Right Mix of Bonding Resins, Additives and Fiberglass Reinforcement Determines The Wheel Life. Metabo® Cutting and Grinding Wheels are Designed and Manufactured in Accordance with Our Most Stringent Specifications So That They, in Combination with Our Power Tools, Achieve The Best Performance and Productivity, Saving Time and Money. Metabo® 616784000 Original Grinding® Long Life General Purpose Depressed Center Wheel, 9 in dia x 1/4 in Thick, 7/8 in Center Hole