SRAM Force D2 PM Left Arm/Spindle Power Meter Crankset Spindle: 28.99mm DUB 165mm Black RoadDUB PWR takes the legendary reliability and accuracy of Quarq technology and inserts it into the crank spindle for clean integration that fits more bikes than ever. Its invisible technology that adds minimal weight and will help you get to the finish line faster. FEATURES DUB PWR spindle based unit measures left side power to calculate total watts Proven Quarq reliability and accuracy Long battery life (400+ hours) to power a season of rides User