XTR has ruled the trails for over two decades, and that legacy continues with the XTR FH-M9111-BS Straight Pull Rear Hub. Using stiffness-boosting straight-pull spokes and machined with precision using the lightest and strongest materials Shimano can find, this flagship rear hub offers impressive stiffness, low-rolling resistance, and the longevity you've come to expect from XTR--all at a very low weight. It's compatible with XTR 12-speed Micro Spline cassettes, and uses a new ratchet drive system that delivers an impressive 7-degrees between engagement points. This particular version is made for bikes with 12 x 148mm Boost rear spacing. For the XTR M9100 group and the XTR rear hub, Shimano designed a new freehub system called Micro Spline. Micro Spline allowed them to move from an 11t to a 10t small cog on their cassettes while adding a 12th gear, increasing the gear range to a whopping 510% on their wide-range 12-speed cassette. The Micro Spline freehub body is made of aluminum instead of steel in order to save weight, but is claimed to be more durable thanks to an increased number of splines that distributes pedaling forces more evenly over a greater area, preventing the cassette from eating into the freehub body. The design also allows for larger-diameter axles inside the hub for a boost of stiffness when you're charging across rough terrain. Shimano also changed their drive mechanism, omitting the traditional pawl system in favor of a system that uses two ratcheting driver plates. These plates glide across each other with minimal friction when coasting, but engage rapidly when force is applied to the pedals. The system offers an impressive 7-degrees between engagement points, and prioritizes reliability above all else. Finally, the XTR rear hub uses cup and cone bearings that are serviceable. That's definitely something you'll want to do on occasion in order to keep them running in top shape. After all, they're a lightweight, race-tuned set of bearings, wh...