Callaway Big Bertha Alpha 816 Double Black Diamond

Some drivers are designed with the ability to make small tweaks that better players like. That's what's going on here, especially with the two positions for the weighted cylinder that the company calls a gravity core. Better players tend to have a consistent impact location, so the gravity core can be placed to line up with that area. The cylinder goes in the heel or toe for a draw or fade, and it can be flipped with the heavy side up or down to match your contact sweet spot. For each loft, that's four ball flights across a tight range (because good players want small changes, not 25 yards of draw bias). Get the settings right, and you'll get your preferred shot shape and maximum energy transfer.