Strong and Rustproof HSSMade 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 service life. Material: Steel Length: 4-12mm length: approx 6.7cm 4-20mm length: about 7.7cm 4-32mm length: about 10cm 4mm twist drill bit Length: about 7.2cm Drilling diameter: 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)