According to DIN 69 111, grinding components with bonded abrasives are comprised of straight, conical, and reduced grinding wheels, abrasive cutting discs, grinding wheels affixed to support discs, cup grinding wheels, bent grinding wheels, grinding segments, mounted points, honing stones and oil stones (Fig. 310). Ignoring form and dimensions, all of these types exhibit the same basic structure made of abrasive material, bond and pore space.
Source: Saint Gobain Abrasives