Callaway Great Big Bertha II. The Callaway Great Big Bertha II Titanium Driver uses Callaway's patented titanium fabrication technology to produce a clubface that has a high (COR) Coefficient of Restitution over a much larger area - allowing even off-centre hits 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. The face angles of the standard lofts range from square in the 8, 9 and 10 degree drivers, to one degree closed in the 11 and 12 degree drivers. The standard lofts have progressive Centre of Gravity (CG) bias, meaning the 8, 9 and 10 degree have slight draw bias, while the 11 and 12 degree have progressively more. CG bias allows golfers the opportunity to square the face better through impact, thereby hitting potentially straighter shots.