With Dura Ace 9000, Shimano introduced an 11-speed crankset with one, 4-arm asymmetric spider that could accommodate both standard and compact chainrings. This trend continues with the Dura-Ace R9100 crank and the patented Hollowglide Dura-Ace R9100 Chainring yields an incredibly stiff and lightweight design that shifts better than anything else on the market, adequately handling the force dished out from Di2 front derailleurs. The forged and precision-machined alloy rings feature Hyperdrive tooth profiles that are engineered to shift with precision and reduce wear.The chainrings are anodized and crafted to perfectly match the finish and shape of the 9100 crank spider for superior stiffness and aesthetics. Inner and outer chainrings are designed as a unit with shift ramps and pins optimized for the best performance so it is recommended to replace them as a set when sizing up or down.