Callaway Great Big Bertha II +. The 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. Long and very forgiving. 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 many golfers the opportunity to square the face better through impact, thereby hitting potentially straighter shots. The clubface efficiency advantage of this "+" version - which does not conform to USGA rules and will be illegal to use in regulated competition golf after January 2008 - has been tested by Callaway's robots to show an increase of two to five yards over the standard version.