Feature:* .* , and practical.* Adopt steel, good flexibility and wear resistance. High precision, tight and stable clamping.* Made of steel, processing by heat treatment and precision grinding.* Suitable for engraving machine, applicable to various specifications of bit tool and chuck.* Highly flexible and wear-resistant.* High accuracy clamping force, good grip stability. Specification:* Material: Stainless Steel* 12mm to 6mm:Inner Diameter: 6mm/ 0.236 inchOuter Diameter: 12mm/ 0.47 inch* 12mm to 8mm:Inner Diameter: 8mm/ 0.31 inchOuter Diameter: 12mm/ 0.47 inch* 12mm to 10mm:Inner Diameter: 10mm/ 0.39 inchOuter Diameter: 12mm/ 0.47 inchPackage Included:3*Bit Route Adapter Sleeve(1*12mm to 6mm,1*12mm to 8mm,1*12mm to 10mm)Please note:- Due to differences between different monitors, the picture may not reflect the actual color of the item. Thanks!-Manual measurement, please allow 1-2mm error. Thank you for your understanding.