The DeWalt DNP617 Centering Cone is well made from thick thermoplastic with a stepped steel shank. The cone is double-sided, so it can be used both above and below the base plate of the milling machine. The only thing it can't do is center a hole with a smaller diameter than the diameter of the shaft used with the cone itself. However, if you use this centering cone for base plates and standard guide bushes, you will have no problems. I would recommend this of several others currently in production except for the small diameter hole centering. I bought mine here at Revain through Tool King and got fast shipping at a great price.