【3+1 Size】1*65mm: The scale on the drill is 4-12. 1*75mm: 4-20. 1*100mm: 4-32. 1 * Centering punch. The drill can process holes of different sizes 【Robust and rust-proof HSS】3+1 pieces countersink drill bits are made of high-quality HSS steel. The titanium coating of the drill can reduce friction and heat, which can also prevent the drill from rusting and thus extend its service life 【Area of application】High-quality and durable HSS steel. The step drill is very suitable for use at home and in construction for drilling holes in a variety of materials such as steel/brass/wood/plastic/thin iron plates/aluminum materials/insulation boards/PVC boards, etc. 【Centering punch】The centering punch is made of impact-resistant alloy steel for easy positioning before drilling and breaking the glass. Positioning and pre-drilling to protect the cone drill