Meet the latest addition to the versatile X0 family, featuring SRAM’s
first carbon downhill race crank and DH-specific derailleur. The rear
derailleur is designed to provide fast and precise shifts for the close
ratio cassettes used on DH race bikes, 4X and jump bikes. The X0 DH
drivetrain provides a new level of crank stiffness and shifting
reliability for the most aggressive terrain. The sub-800g (claimed
weight) carbon crank has been developed and proven by top World Cup pros
in the most extreme conditions imaginable.

In 2010 Sam Hill used a prototype version of the XO DH carbon cranks at Mont-Sainte-Anne to secure his world championship.
SRAM's XO Chainguide should pair up nicely with the new XO downhill-specific carbon cranks.
The DH-specific XO derailleur is designed to run exclusively with cassettes featuring a 28T cog or smaller.