* Combine any length Quarq DUB crank arm with DFour DUB power meter for Shimano® R910011-Speed groupset. * Designed for R9100 chainring. Compatible but not aesthetically pleasing with Shimano’s R8000 chainringsand Shimano's R700 chainrings.* Magic Zero: Automatically check and recalibrates your power meter to ensure it is always accurate.* AXS™ app: Easily update firmware and view power meter metrics.* OmniCal: Swap chainrings without affecting accuracy.* 10K TEMPERATURE COMPENSATION: Each power meter is programmed with over 10,000 data points to eliminate temperature effects on power measurement.* For use with Red D1, Force D1, or Quarq D1 crank arms