Callaway Hawkeye VFT. Callaway Hawkeye VFT (Variable Face Thickness) irons were the top of the range Callaway product when they were launched. A unique titanium casting process creates an internal weight pocket inside each Hawk Eye VFT iron. This pocket is then filled with the tungsten weight matrix, a dense mix of tungsten spheres and molten metal that accounts for an average of 48% of the clubhead weight and only 30% of the clubhead volume. This creates enormous stability and makes them one of the easiest clubs to hit. The low centre of gravity in the Callaway Hawk Eye VFT irons also helps launch shots higher without losing any distance. Callaway's current equivalent model - the Fusions - use the same titanium/tungsten principle to achieve usability.