Features DURABLE MATERIALS: Made of 40Cr and carbon steel materials, with carburizing and quenching process, high hardness and strength. HIGH ACCURACY: Inner hole grinding treatment, has high concentricity, suitable for high accuracy machine tool processing. CLAMPING RANGE: The clamping range of the extension rod is 1‑7mm, standard in size, and it is suitable for ER11 collet. INTEGRATED FORMING: The inside and outside of the tool holder are integrally formed, fine control processing, with stable performance. WITH WRENCH: Equipped with a wrench, stable in processing, and can effective vibration suppression. Specification: Item Type: Extension Rod Product Material: 40Cr + Carbon Steel Hardness: 45-46HRC Head Diameter: Approx. 19mm / 0.75in Clamping Range: Approx. 1-7mm / 0.04-0.28in Adapter Collet: ER11 Thread Type: A Tool Shank Diameter: Approx. 16mm / 0.63in Package List: 1 x Tool Holder 1 x Wrench Note:1. Incorrect assembly may damage the accuracy of the nut and spring2. Only the matching collet chuck can be used to assemble the nut3. Do not clamp tools that exceed the clamping range Package List 1 x Tool Holder 1 x Wrench