SRAM Apex AXS Wide Left Crank Arm and Power Meter Spindle Assembly - 172.5mm, 12-Speed, DUB Spindle Interface, Black, D1Accurate, reliable power measurement is practically a requirement these days, and the Apex AXS crankarm power meter upgrade is the easiest way to get precise power numbers. With the tech hidden inside the DUB spindle, it fits almost any bike while remaining stealthy. 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 Waterproof