Callaway Big Bertha Hawkeye VFT Pro Series. The Callaway Big Bertha VFT fairway woods feature Callaway's Variable Face Thickness (VFT) Technology which allows manufacture of a very thin - yet strong - clubface. One of the earliest fairway woods to benefit from the 'trampoline effect' whereby the face 'gives' slightly on contact with the ball and then, in a fraction of a second, restores itself, catapulting the ball off for increased distance. The Big Bertha Hawk Eye VFT Pro Series Titanium Fairway Woods are designed without the draw bias of the standard VFT woods, allowing better golfers to control the flight and trajectory of their shots.