Japanese craftsmanship soars into the future with Shimano's new 12-speed groupset, and while the cassette, hub, and rear derailleur seem to be getting all of the attention, we think that the new XTR FC-M9120-1 Crankarms belong in the limelight too. Like the all-new groupset, these Hollowtech II crank arms aim to bring your drivetrain into the future with a lighter and stiffer design, and simple to change direct-mount chainrings with a single key release, allowing you to feel things out with your new 12-speed configuration, finding the perfect chainring ratio for you. If you're a little confused by Shimano's offerings of both the FC-M9120 and FC-M9100, you're not alone. With two offerings in this top-tier package, the differences may be difficult to spot at first glance. Shimano builds the M9120 with a beefier, more robust design than the XC-oriented 9100, ideal for riders charging hard and having up-close-and-personal encounters with rowdy sections of trail that give your crankarm the occasional bash. On top of the beefier construction, the M9120 crankarms boast a wider Q-factor that lands in at 168mm, in comparison to the 158mm of the 9100. This wider Q-factor increases stability when you're descending at high speeds, and offers a bit more chainstay clearance for beefier 148-millimeter Boost spacing in the back. As its name suggests, this particular XTR M9120 Crankset is intended solely for bikes with Boost 148-millimeter rear axles, with its 52 millimeter chainline reflecting the outboard move to accommodate Boost axle spacing. The crank arms come alone, without chainrings, but can be paired up with either one-by or two-by options in a huge range of sizes to best suit your riding needs. Additionally, Shimano is offering the XTR 9120 in a range of sizes from 165mm to 175mm, so shorter riders, or those with gravity-oriented appetites who want a little more clearance, can be decked out with the perfect crank length, too.