Features: Make from High carbon steels, High strength, high hardness, firm structure. Spirals straight thread, more convenient clamping, faster replacement speed and higher clamping force. The is smooth, no scratches, and stable performances. Used for motor extension rod, replaceable drill chuck, perfectly fit with chuck of various straight shanks tool. Suitable for lathes, drilling machines, boring machines, boring machines, fixtures, drills, and milling cutters. Specifications: Materials: High carbon steels Inner diameter option: 3mm(0.12inch)/3.175mm(0.125inch)/4mm(0.16inch)/5mm(0.20inch) Length: about 50mm/1.97inch Package Includes: 1Pc Collet Chuck Spindle Extension Rod note: Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. Due to difference between different monitors, the picture may not reflect the actual color.