29 sizes: 3 standard size step drill bits have the following 32 sizes: 15 steps: 4-32mm (4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm, 24mm, 26mm, 30mm, 32mm.); 9 pitch: 4: 4mm (4mm, 4mm, 6mm, 4mm, 6mm, 8mm, 4mm, 8mm, 4mm, 6mm, 8mm, 4mm, 6mm, 8mm, 4mm, 4mm, 6mm, 8mm, 6mm, 8mm, 10mm, 10mm 2mm, 14mm, 16mm, 18mm, 20mm 5 steps: 4-12mm (4mm, 6mm , 8mm, 10mm, 12mm) A variety of drill bit sizes are perfect for your needs and save you time Premium Material: These step drill bits Bits are made of heat treated 4241 high speed steel with titanium nitride coating .Titanium coating to reduce friction and operate cooling, can effectively prolong the service life.Ladder structure: one drill bit can drill holes of different specifications, no need to buy multiple drill bits, saving money , space and money.Spiral slot: allows for faster and smoother cutting and tri-flat shank to ensure a firm grip.Triangular round shank: can be easily inserted into a drill, drill press and a drill Suitable for: The step drill set can be used for workpieces with a hardness of less than 25 and a thickness of less than 5 mm.Suitable for a variety of materials, such as carbon steel, sheet metal, insulating panels, PVC panels, wood, etc. They also make it possible to enlarge existing holes. Not recommended for stainless steel. Total Length: 4-32mm: Approx. 102mm. 4-20mm: approx. 76mm. 4-12mm: approx. 66mm. Shipping Quantity: 3 spiral step drill bits.