Foredom Miniature Carbide Ball Set, Style AK211, 7 piece. These miniature carbide ball burs come in a plastic case. They are ideal for use on hard wood and most metals including stainless steel, steel alloys, cast iron, etc. 2.35mm (3/32") shank. 1-3/4" overall length. 100000 RPM Max Speed. Made in USA. Includes bits 10221, 10222, 10223, 10224, 10225, 10226 and 10227.