Features Wide Application: This collet chuck extension rod is suitable for deep machining and solves the need for deep machining. Suitable for all kinds of milling machines, which brings great convenience to people's work. It is particularly practical and easy to Stable Structure: The collet chuck extension rod is made of 40CR material, which is repeatedly tempered and forged, and has a very high hardness and stable structure. Fast Speed: The maximum speed of this collet chuck extension rod is 8000 rpm for the R40 shank in the R8 chuck. High Stability: Using collet chuck tool holder to increase stability, avoid carbide shank breakage, and increase tool feed rate and cutting volume. All working parts are accuracy polished and hardened Accurate Craftsmanship: The collet chuck extension rod has high accuracy performance and can be tightly fixed on the drill bit, which can guarantee the user safe use and stability. Specification: Item Type: Collet Chuck Extension Rod Material: 40CR Model: R8 ER25 (M12) R8 threaded shaft Drawbar: M12 Applicable To: R8 special purpose machine ER25 collet chuck nut Total Tightening Accuracy: ≤ 0.005 Rounding: < 0.8 u Body Accuracy: 0.001 Carburising Depth: > 0.8mm / 0.03in  Surface Roughness: > 0.8mm / 0.03in  Standard Speed: 8000 rpm Package List:1 x Collet Chuck Extension Rod 1 x Storage Box Note:The presence of errors in the spindle of the user's machine also has a significant impact on accuracy when testing. Therefore, you need to ensure that the spindle accuracy of the user's test machine must be very high. In addition, make sure that the accuracy of the ER collet must be very high. Many ER collets are marked at 0.0005inch and many of them do not achieve this. Package List 1 x Collet Chuck Extension Rod 1 x Storage Box