Features Wide Application: This collet chuck extension rod is suitable for deep machining, solving the need for deep machining. Suitable for all kinds of milling machines, which makes people's work much easier. It is particularly practical and easy to use Stable Structure: The collet chuck extension rod is made of 40CR material, which is repeatedly hardened and forged, which has very high hardness and stable structure. FAST SPEED: The maximum speed of this collet chuck extension rod is 8000RPM for R40 shank in R8 chuck. High Stability: Using a collet chuck tool holder to increase stability, avoid carbide shank breakage, and increase tool feed speed and cutting volume. All working parts are precision polished and hardened Precise Craftsmanship: The collet chuck extension rod has high accuracy and can be firmly attached to the drill bit, which can guarantee users 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 machine ER25 collet nut Total Tightening Accuracy: ≤0.005 Rounding: 0.8mm/0.03in Surface Roughness: > 0.8mm/0.03 inch Standard speed: 8000 rpm Package list: 1x 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 testing accuracy. Therefore, it must be ensured that the spindle accuracy of the user's test machine must be very high. In addition, it should be noted that the accuracy of the ER collet must be very high. Many ER collets are marked .0005 inch and many of them don't reach that. Package List 1 x Collet Chuck Extension Rod 1 x Storage Box