Callaway 2004 Big Bertha. Callaway 2004 Big Bertha irons are aimed at mid to high handicappers. At first glance, not hugely different to the 2002 Big Bertha irons, the main difference is that the sole is slightly thinner which reduces dragging, allowing the clubhead to slide more easily through thicker grass. With a constant-width sole, every club in the set has the same width to position the centre of gravity low and deep, creating a uniform feel and making them extremely easy to use. Callaway's 'Notch' weighting ensures the club head is much less likely to twist on off-centre hits. With their deep cavities and a confidence-inspiring top-line, these really are very easy clubs to use.