1Can improve the rigidity of the tool and extend the life of the blade. 2Convenient clamping, automatic centering, the height of center is more accurate center. 3Suitable for U drill, taper shank drill, extension rod, milling cutter rod, inner diameter cutter rod, straight shank cutter and so on. 4D40 is applicable to SBHA25-40 and SBHA32-40. 5Made of high-quality steel 40Cr, high hardness, high strength, not easy to break.