This mini drill chuck adopts polishing technology on the surface, so it features anti-oxidative, waterproof and anti-corrosion. The drill chuck is made of high quality metal, hardness and weresistance, durable in use. Drill chuck comes with chuck key to adjust the chuck for proper tightness, convenient to install and operate. Drill chunk can be widely used for lathe, electric drill, milling machine and more. The set can help you complete your work quickly. Drill chuck has standard size, suitable for your devices. Clamping range: 0.3-4mm, outer diameter: 21.5mm/0.85in, brass base size: length: 20mm/0.79in, hole diameter: 3.175mm/0.13in.