Callaway steelhead xr graphite golf irons are fitted with matrix ozik program f15 shafts to increase performance callaway has used a modern hollow bore through design and next generation 360 face cup technology to increases ball speed and increase its moi callaways engineers have taken weight out of the hosel and re position the centre of gravity to get the optimum trajectory the new steelhead xr golf irons are more efficiency on both centre hits and mis hit shots this provides more distanc