SRAM XO BB30 4228T Crankset w Bottom Bracket. The SRAM XO BB30 2x10 speed crankset is a tour de force performer for cross country and all mountain endeavors. The XO features carbon fiber crank arms that deliver exceptional stiffness and strength while keeping the weight to a minimum. SRAM's renowned X Glide chainring technology ensures smooth shifting, even under load, while their CNC machined aluminum construction ensures that they're lightweight and strong. This crankset features 4228T chainrings and includes a SRAM BB30 bottom bracket.