We engineered a precise amount of tungsten into our internal standing wave technology, allowing us to uniquely position the CG in each iron. The performance benefits? Lower CG in long irons promotes easy launch and high, long carry, and higher CG in short irons means lower, more controllable flight. A slightly smaller head, slimmer topline, and less offset promote the kind of keen feel and workability that better players want. The result is the most premium, high-performance iron ever to bear the Callaway name.