SRAM Apex AXS Wide Left Crank Arm Power Meter Spindle Assembly - 160mm 12-Speed DUB Spindle Interface BLK D1SRAM Apex AXS Wide Left Crank Arm and Power Meter Spindle Assembly 160mm 12 Speed DUB Spindle Interface Black D1. Accurate 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