Upgrade your Rally 110 to a dual-sensing power meter, and analyze more than just watts to see exactly how your pedaling style generates the force that moves you. When paired with Rally 110, the upgrade spindle turns your system into a Rally 210 power meter, providing left/right balance data and cycling dynamics. The spindle is even transferable to other Rally 210 pedal bodies so you can have power for all your rides.Cycling dynamics display where you re generating power throughout the pedal stroke and show left/right balanceSee where you apply force on the pedal to ensure proper cleat position and track seated time vs. standing time to see how position changes efficiency Garmin Rally 110/210 Dual Sensing Upgrade Spindle Pedal Small Part UPC: 753759349646