Callaway Golf Men's XR Irons Set Revolutionary Ball Speed From Cup 360 Our improved face cup technology even acts like a spring on shots hit low on the face to increase ball speeds; The speed is higher at every other impact location on the face too Lower CG, More MOI and Ball Speed The Internal Standing Wave is the ultimate team player; It's refined the way that we lower CG, increased MOI and gives the face cup the freedom to flex for more ball speed New Construction And Shape An iron built for speed needs a different level of refinement and attention, in this case a 2-piece construction that includes a dual heat treatment; It's precise, meticulous craftsmanship that XR deserves