Callaway Great Big Bertha Tungsten Titanium. Callaways crème de la crème when they were launched - the Great Big Bertha irons retailed at over £1500. A large, ultra-light titanium head with a very heavy - 40% of the weight, but only 15% of the volume - tungsten insert in the sole makes for a very forgiving club which gets the ball airborne early. Callaway's latest current-model equivalent - the Fusions - use the same titanium/tungsten principle to achieve usability.