Made of Carbon Steel material with black coated.A chuck require a key to provide the necessary torque to tighten and loosen the jaws.Allows you to keep your drill bits firmly in place for difficult jobs.Great for replacing lost or worn out drill chuck keys. Specifications:Color: BlackMaterial: Carbon SteelSurface Treatment: BlackeningGear Teeth Quantity: 11Key Diameter: 3mm / 0.12 inchGear Diameter: 11.2mm / 0.44 inchTotal Size: 57 x 35mm / 2.24 inch x 1.38 inch(L*W) Package Content:1 x Chuck KeyChuck Key Selection Method:For 0.3-4mm drill chucks: key diameter about 3mm, gear diameter about 11.5mmFor 0.6-6mm drill chucks: key diameter about 5mm, gear diameter about 15mmFor 1.5-10mm drill chucks: key diameter about 6mm, gear diameter about 12.5mmFor 1.5-13mm drill chucks: key diameter about 6mm, gear diameter about 17.5mmFor 5-20mm drill chucks: key diameter about 9mm, gear diameter about 25mmFor 1-13mm, 3-16mm, 1-16mm drill chucks: key diameter about 8mm, gear diameter about 21mmThe above data is for reference only, only suitable for general models, except for special models