Mizuno JPX 900 Hot Metal

How do you get the kind of ball speed typically reserved for an iron with a cupface or thin-face insert without having either? Mizuno uses a special kind of steel called Chromoly 4140M—a material used in high-tech bicycle frames and the body of solar cars. Its high strength-to-weight ratio allows for Mizuno's thinnest iron face yet—two millimeters. The thin face combined with a deep undercut promotes rebound off the face. A rib structure inside the topline stabilizes the frame for optimal feel despite the thin face.