3+1Size1*72mm: the scale on the drill bit is 4-12. 1* 72mm: 4-20. 1*102mm: 4-32. 1*72mm twist drill bit. The drill can handle holes of different sizes HSS Sturdy and RustproofMade of high quality HSS, it cuts through thin materials quickly. HSS provides extreme durability, and the drill bits are rustproof. At the same time, our drill bit is suitable with electric screwdriver ApplicationStep drill bit suitable for DIY, home and construction. It is very suitable for drilling holes in a variety of materials like steel/brass/wooden/plastic/thin iron plate/aluminum materials/insulation plate/PVC plate, etc. Only suitable for ordinary aluminum, iron and steel plates (thickness can not exceed 4mm, hardness is less than 25HRC), not for stainless steel Twist Drill BitWith 4mm HSS 6542 Twist Drill Bit can pre-drill the materials, which makes the step drill bit less easily damaged than the ordinary step drill bit. Note: Oil stepped bits before each use to maximize life. Note: 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. Sold by-Dadangjia