If you're running a SRAM one-by drivetrain but aren't ready to surrender your top speed gears, the HED XD Driver Body will convert your wheels to accommodate a 10t cog. After all, what good is the simplicity and lower weight of a one-by setup if your top speed is hampered? The XD Driver features the same five pawl engagement as HED's standard 545 freehub bodies, so the engagement doesn't suffer, but your opponents will.