For use with grinders 1/8" blade thickness, Type 27, A24R grit is designed for cutting For use with grinders. 1/4" blade thickness, C24R grit is designed for grinding concrete, masonry, cast iron, ductile iron, and other masonry materials. High grain concentration. Proprietary wheel design. 3 full sheets of glass in every 1/4" wheel and 2 full sheets in every 1/8" wheel.