A1257H Flexovit by Bisco Tool Supply areType 27 Flexovit Depressed Center Grinding Wheels for Concrete and Masonry. These Heavy Duty Grinding Wheels are designed for concrete and masonry applications. Made with Silicon carbide Grain, the C24/30P also offers fast grinding on nonferrous metals. 4-1/2"x1/4"x5/8-11 Flexovit Heavy Duty Depressed Center Grinding Wheel for Concrete, Masonry. Flexovit Industrial Abrasive Wheels. Made in the USA by Flexovit High Quality Industrial Abrasive Products. Sold in box quantities of 10.