3+1Size1*65mm: the scale on the drill bit is 4-12. 1*75mm: 4-20. 1*100mm: 4-32. 1* centering punch. The drill can handle holes of different sizes HSS Heavy Duty and Rust Proof3+1 pcs Countersink Drill Bit Step Drill Bit is made of high quality HSS steel. The titanium coating on the bit can reduce friction and heat, which can also prevent the bit from rusting, extending the service life ApplicationHigh quality and durable HSS steel. Step drill bit is very suitable to use in home and construction to drill holes in a variety of materials like steel/brass/wooden/plastic/thin iron plate/aluminum materials/insulation plate/PVC plate etc. Centering PunchThe centering punch is made of impact resistant alloy steel for easy positioning before drilling and breaking glass. Positioning and pre-drilling to protect the conical drill