Callaway Fusion Individual Iron w/Steel Shaft: The Big Bertha Fusion Irons deliver everything you've come to expect from Callaway but with a few new twists. The most untraditional, traditional-looking irons you'll ever play. Callaway Golf's weight distribution technology, designed for Big Bertha Fusion Woods, is now available in irons, featuring Tunite alloy, a TPU SenSert and a lightweight 6-4 titanium face insert. The Tunite cradle allows 77% of the mass to be positioned around the extreme perimeter of the iron for ultra-high MOI and a low, deep CG; the TPU SenSert helps reduce vibration for great feel, plus eliminating the hollow sound and feel of an oversized cavity-back for a crisp, responsive sound; the lightweight 6-4 titanium face insert is 22% lighter than a comparable steel face allowing the weight to be distributed around the perimeter for faster ball speed, greater feel and a larger sweet spot.