Arm Material: aluminum Arm Length: 160, 165, 167.5, 170, 172.5, 175, 177.5mm Chainring Sizes: 54/40t, 52/36t, 50/34t Bolts: 4 Rings: 2 Our bicycle's crankset can be our saving grace, but it can also be our downfall when it comes to wasting watts. Thankfully, the Dura-Ace FC-R9200 Crankset from Shimano is in the business of ensuring no portion of our pedal stroke is wasted. This crankset effectively transfers all of the efforts we put into cranking out pedal strokes into the drivetrain, but it also makes for the fastest and most precise front shifting available. Its HollowGlide structure cuts weight while maintaining strength for improved power transfer, and we like the optimal balance Shimano strikes between stiffness, weight, strength, and rotational performance. We're happiest when stiffness and shifting precision is maximized, and that's what this crankset can offer.