Size: Size 1: length 7 cm, meter (mm): from 4 to 12: 4,5,6,7,8,9,10,11,12 Size 2: length 7 cm, meter (mm) : from 4 to 20: 4,6,8,10,12,14,16,18,20 Size 3: length 10 cm, meter (mm): from 4 to 32: 4,6,8,10,12, 14,16,18,20,22,24,26,28,30,32. With 4mm Twist Drill: The 4mm twist drill can pre-drill the step drill, which makes the step drill less easily damaged than the ordinary step drill. Material: Stepped drill bits suitable for DIY, home and construction. It is very suitable to use for drilling holes in a variety of materials like steel, brass, wood, plastic, thin iron plates, aluminum materials, insulation plates, PVC plates, etc. Only suitable for ordinary aluminum, iron and steel plate (thickness can not be more than 4mm, hardness is less than 25HRC), not for stainless steel. Robust and durable: Set of 3 Milling Cutter Drill Bit Etage is made of high quality HSS steel and coated with titanium to reduce friction and heat. Attention: If you have any questions about the quality of our 3PCS Step Drill Bits, please feel free to contact us by email. Your satisfaction will be our greatest pursuit. Product description 3PCS HSS Step Drill Bits (4-12mm / 20mm / 32mm) with 4mm Twist Drill - High speed steel auger made of high quality hardened steel. - The coating uses a titanium alloy coating to reduce friction and heat. - Suitable for DIY, home, and general construction / engineering. Can be used for wood, sheet metal, steel and other surfaces. Note --- Before use, it is necessary to install a fixed clamping hexagonal rod to prevent the occurrence of swaying and tension in the groove, etc., to avoid the risk of cracking. Fall and so on. Apply ----- Step drill bits suitable for DIY, home and construction. The material is only suitable for ordinary aluminum, iron and steel plate (thickness can not be more than 4mm, hardness is less than 25HRC), not for stainless steel. High quality - HSS hex shank drill is made of high quality hardened steel, not easy to damage. - With titanium coated to reduce friction and heat. Do not use the center punch, compared with the ordinary twist drill is not easy to break. The Design of Two Flutes - Dual flute design provides faster, smoother and cleaner cuts. Practice - Suitable for DIY, home and general purpose building / engineering. Can be used for wood, sheet metal, steel and other surfaces. including steel, brass, wood, plastic, etc. Product Specifications: Material: Steel Length: 4-12mm length: about 7.2cm 4-20mm length: about 7.2cm 4-32mm length: about 10.2cm 4 mm twist drill Length: about 7.2 cm Size: 4-32mm (4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm, 24mm, 26mm, 28mm, 30mm, 32mm) 4-20mm (4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm) 4-12mm (4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm) Advantage - 4mm Twist Drill is wider than HSS step drills. It can pre-drill the HSS step drill bit, which effectively reduce the damage of HSS step drills when drilling and extend the life of HSS step drills. The package includes 1 x 3PCS HSS Taper Drill Bits (4-12mm / 20mm / 32mm) 1 x 4mm Twist Drill 1x Nylon storage bag