Description:Unique ladder structure allows this step drill bit to drill out a variety of specifications of apertures,which has perfect practicability and versatility.Compared with ordinary twist drill bit this step drill bit is harder to break and has smaller shaking during drilling and needs no center punch,which is easier and more convenient to use.These straight flute step drill bits are mainly made of high speed steel.The length of this set is 9.3cm,the width is 7.7cm and the height of it is 2.1cm,and there are the specifications of 3-12mm,4-12mm,4-20mm for you to choose.This set can be used in automobile processing,aerospace,sheet metal processing,electrical installation and maintenance and other industries.Item Name: Straight Flute Step Drill BitsMaterial: High Speed SteelType: Straight FluteStep Spacing: 5mmHandle Type: Hexagon HandleHandle Diameter: 6.35mm (1/4 inch)Cutting Diameter: 3-12mm(3mm,4mm,5mm,6mm,7mm,8mm,9mm,10mm,11mm,12mm),4-12mm(4mm,6mm,8mm,10mm,12mm),4-20mm(4mm,6mm,8mm,10mm,12mm,14mm,16mm,18mm,20mm)Features: Firm,HSS,DurableSize Details: 3-12mm: Length: 78mm/3.07,Head Length: 53mm/2.09,Steps: 10 Steps (Approx.)4-12mm: Length: 66mm/2.6,Head Length: 41mm/1.61,Steps: 5 Steps (Approx.)4-20mm: Length: 75mm/2.95,Head Length: 50mm/1.97,Steps: 9 Steps (Approx.)Handle Length: 24mm/0.94 (Approx.)Notes:Due to the light and screen setting difference,the item's color may be slightly different from the pictures.Please allow slight dimension difference due to different manual measurement.Package Includes:3 x Step Drill Bits (3-12mm,4-12mm,4-20mm)