This Faithfull Mounted Stones Set comprises 5 miniature grinding wheels, ranging from 13mm to 24mm in diameter with 6mm (1/4 inch) shanks for compatibility with most electrical and cordless drills. The grinding wheels are ideal for sharpening and grinding steel, metals, glass, ceramics and plastics. Shapes include tree, cone, large cone, cylindrical and ball. Maximum speed 30,000 / min.