Model 650W 6'' DIA Coolant-thru Air Chuck. It has Special hardened and ground Jaws to grip the customer’s part with a 39.74mm body. Jaws are made of 1018 steel case hardened and ground to 58/63 Rc. with a step machined in it to act as the part stop. Also it has a Special Face mounted Spyder locating base for Model 650; it has been hardened & ground to hold the customers special dressing ring. The customer wanted to be able to dress their grinding wheel in close proximity to the part that they grind with this chuck.