The SRAM RED AXS Aero power meter kit builds power measurement directly into a direct-mount, aerodynamically profiled chainring rather than adding it as a separate spindle or spider component. X-SYNC wide-narrow tooth profiling keeps the chain locked in through rough sections, and the whole assembly stays light and stiff without the drag penalty of bolting power-measuring hardware onto the outside of the crank. What Our Gearhead(R) Experts Are Saying:"I've watched my left and right power numbers split apart mid-interval and used that to actually correct a stroke imbalance I didn't know I had. A single number never would have told me which leg needed the work."