M35 co high speed steel step drill bits, higher quality and more durable than HSS 4241 step drill bits. High speed cobalt steel along with titanium coating ensures extreme durability, it will stay new and shiny for years to come. Hex shank diameter: 6.35mm. No need center punch, compared with ordinary twist drill bit, it is not easy to break and it can be used for deburring, chamfering and opening hole. M35 co high speed steel step drill bits, higher quality and more durable than HSS 4241 step drill bit. Effective as a great cobalt drill bit. Made of super strong HSS steel for extra durability and longer life. Non-walking drill tip provides fast and smooth drills on steel sheet, aluminum sheet, wood board, plastic board, etc. (The board should be smaller in thickness than the height of the step drills).Size:4-20mmFeatures:Material: High Speed Steel, Co (HSS co M35)Surface Treatment: Titanium CoatedHex Shank Diameter: 6.35mm/1/4"Dimension: 4-20mm (4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm,