KEO 50046 Cobalt Steel Single-End Countersink Set, Uncoated (Bright) Finish, 6 Flutes, 60 Degree Angle, 1/4″ – 1″ Body Diameter. Cobalt steel tools are similar to high-speed steel, but with more cobalt for improved performance when cutting harder metals such as stainless steel or nickel alloys. Uncoated tools feature just the base substrate without any additional treatment or coatings and are suitable for a wide range of applications. Cobalt sets include one piece each of: 1/4, 3/8, 1/2, 3/4, 1 body diameter with a particular included point angle. ISO 9001:2008 certified. Thanks for looking at our listing and supporting our small family business!