Description1. Made of high-speed steel. HSS(High Speed Steel) enables the drill body harder and can keep a longer drilling life. 2. With the twisted design, it can improve cutting accuracy by centering the tip. It can avoid displacement of the drill bit during work, and at the same time remove debris and particles faster and easier.3. Suitable for processing non-ferrous metals, such as copper and aluminum, and also suitable for hard plastics. When it cannot penetrate, try to adjust the RPM.4. Please keep cool and gentle using, the working life of the twist drill bits can be largely prolonged by proper usage.SpecificationsMaterial: HSS (High Speed Steel)Shank Type: Round ShankTwist Drill Bits Diameter: 4mm / 0.16-inchDrill Bit Length: 105mm / 4.13-inchShank Diameter: 4mm / 0.16-inchTotal Length: 160mm / 6.