Depressed Center Wheels, Abrasive Wheel Type Type 27, Abrasive Wheel Diameter 5 In., Thickness 1/4 In., Arbor Hole Size 7/8 In., Abrasive Material Aluminum Oxide, Abrasive Grit 30, Max. RPM 12,200, Series High Performance, Grade Very Coarse, Application Stainless, Contaminate Free. Featuring high-performance aluminum oxide grain for long life and aggressive material removal, DEWALT Type 27 HP Stainless Steel Grinding Wheels are built to grind heavy metals, such as stainless steel and super alloys. 3 full sheets of fiberglass ensure durability and safety. A proprietary material mix ensures long wheel life.