From X Factory:
When X Factory released their Infinity parts for the X Ray XB2 something was missing: the dirt spec tower. Well, here it is! The Infinity dirt spec tower matches the X Ray geometry perfectly and bolts right up, but X Factory’s tower is stronger, stiffer, 4mm carbon fiber, less flexible than the 3.5mm kit tower, and all that is important in outdoor racing with its larger jumps and higher speeds.
Made from U.S. carbon fiber in X Factory’s new Michigan shop, the thicker tower is different from standard in one respect. The kit tower is installed with bolts that thread into the CF. Use the same bolts with the Infinity tower, but secure it with lock nuts provided with the tower.