Shimano's 11 speed cranksets utilize a proprietary 4-arm bolt circle diameter that is asymmetric.Though there are aftermarket options for replacement or changing tooth count, premier level Shimano shifting requires the patented tooth design, pick-ups, and ramps of the 4-arm Hollowglide large chainring. This lightweight construction is inherently stiff, which only gets amplified when bolted to the integrated spider of the Hollowtech II drive side crank arm. Stiffness far exceeds the load of mechanical drivetrains, as the rings were designed for the power of the Di2 electronic front derailleur.