Features: 1.Specification: Shank Diameter: 1/4"(6mm) ; Head Diameter: 20mm/0.78inch （The actual size measured by hand is a little smaller as shown in the figure.） 2.Material：The grinding head is made from Aluminium Oxide, which has high hardness, toughness, and good stability. 3.Compatibility: Compatibility: 1/4 inch round shank can fits electric rotary tools, drill, grinder and pneumatic power tool. 4.Cylindrical shape: Suitable for surface and edge grinding, form grinding. 5.Suitable for grinding of medium and high tensile strength metal materials. 6.Widely used for rough grinding of ordinary steel, such as carbon steel with low hardness, general alloy steel, malleable cast iron, hard bronze, cutting tools, workpieces, etc. Notice： 1.