Features Faster And Smoother Cutting --- The four spiral grooves and cutting blades of this step drill bit ensure quicker and smoother cutting, making it feel like cutting through butter. High Speed --- Made from high speed design, this step drill bit is perfect for drilling stainless steel, metal sheets, wood, plastic, aluminum, copper, and other metal plates. High Hardness --- With a surface hardness of 89HRC, this step drill bit can cut through harder materials and achieve higher cutting speeds. Material --- The step drill bit is made from M35 cobalt steel, which is known for its excellent heat resistance, strength, and durability. Diameters --- Designed to drill holes in nine different sizes ranging from 4mm to 12mm, and it features a 1/4‑inch shank for easy compatibility with various drilling machines. Specification: Item Type: Step Drill BitsMaterial: M35 CobaltHole Diameter: 4-5-6-7-8-9-10-11-12mm/0.2-0.3-0.4-0.5in Shank Diameter: 1/4 inch Package List:1 x Step Drill Bit 1 x Storage Box Package List 1 x Step Drill Bit 1 x Storage Box