Mercer Abrasives 620060-25 Type 27 Depressed Center Grinding Wheels 4-1/2-Inch by 1/4-Inch by 7/8-Inch, 25-Pack Type 27 depressed center grinding wheels Size: 4-1/2-Inch by 1/4-Inch by 7/8-Inch 25-Pack Metal grit Available in all different sizes and grits