High speed steel construction with a titanium nitride coating. These cone drill bits are strong and durable, and the TiN coating reduces friction and heat, helping the bits stay cooler for longer tool life. 29 size range from 4 mm to 32 mm. The time saving design eliminates the need for constant bit changes, letting you drill or enlarge holes of different sizes smoothly and efficiently. Smooth bore for fast, clean drilling on a variety of materials, including steel sheets, aluminum sheets, wooden boards, plastic boards, and more. Achieve accurate results with every use. Wide applications. Ideal for sheet metal work, sink installation, auto components, and more. Suitable for cutting through boards, aluminum, insulation boards, and PVC panels for versatile project capability. Use scenarios - Enlarge or create precise holes in metal or plastic electrical boxes for wiring, conduits, or fittings. - Drill or widen holes in sheet metal panels for mounting brackets, fasteners, or auto components. - Create clean holes in wood, PVC, or insulation boards for DIY cabinetry, home upgrades, or hobby projects.