Features: 1Internal cooling through hole and the central through hole design are conducive to water cooling 2Anti?vibration and more anti?bending, which can help for reducing the use of long knives 3Advanced vacuum quenching furnace, can realize carbon and oxygen co?permeation to increase the hardness of the tool shaft and enhance the lifespan 4Hex nut, convenient for clamping, loading and unloading more convenient, possess high rigidity, strong clamping force 5Can reduce the use of lengthened tools, good for reducing costs and improving efficiency 6UM type ER extension rod is tightly fitted with fine teeth. The size of the ER chuck used for mounting is different, and the size of the nut is also different 7Accurately ground outer diameter of the extension rod and other parts to eliminate the imbalance and increase the stability during cutting Package included: 1 x Collet Chuck Holder