Callaway XR Irons Steel Shafts Right Regular Speed Step 80 5-PW+SW Revolutionary Ball Speed From Cup 360 Callaway have improved their face cup technology to act like a spring on shots all across the face to increase ball speeds at every impact location. 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. It’s precise, meticulous craftsmanship that XR deserves.