The wheels are generally made from a composite material consisting of coarse-particle aggregate pressed and bonded together by a cementing matrix (called the bond in grinding wheel terminology) to form a solid, circular shape, including the shape of 1A1, 1A1R, 1V1. 6A2, 9A3, 12A2, 12V2, 14EE1, 9EE1 types for tool grinding wheels.