The Callaway Great Big Bertha 2 driver is designed to add forgiveness off the tee. The titanium construction allows it to be larger than it predecessors with a hotter face. The COR of this driver, the measure of how efficient it is at transferring energy to the ball, is increased by using stronger, thinner titanium. The larger clubhead increases Moment of Inertia. This reduces the twisting of the clubhead when the ball is struck off-center so you're not penalized as much when you don't hit a shot perfectly.