Kent 10pcs Mix Kit Tungsten Carbide Rotary Burrs, 1/8" (3mm) Shank 10pcs Mixed Kit, Tungsten Carbide Rotary Burrs, 1/8" (3mm) Shank 1/8" (3mm) Diameter Round Shank 1/4" (6mm) Head size, 1-3/4" (45mm) Overall Lenght Various shapes included, such as spheres, cylinders, bullets, needles, etc. 1/8" (3mm) shank for electric rotary tools, drills, high speed die grinders, and flex shafts