SRAM XO
Designed for World Cup performance and everyday durability, the XO group switches to a 2x10 or 3x10 drivetrain. Technology from the XX group has trickled down into the XO group, with shifting becoming almost instantaneous thanks to smart engineering by SRAM. An XO-branded carbon crankset weighs 788 grams and is claimed to be 10 to 15 percent stiffer than XX, but weighing only 60 grams more. Over three days of testing, the components worked flawlessly, shifting crisply and consistently, regardless of conditions or gearing.(www.bicycling.com)