The EX1 drive train was designed specifically for the demands of electric-assist mountain bikes: a wide gear range with bigger jumps between gears and sturdy components to handle higher torque loads. Liberal use of features found on SRAM's high end MTB parts provide high value, quiet operation and ease of service. - X-Sync (wide-narrow) tooth profiles for great chain management - Compatible with Bosch mid-drive E-bike systems - Material: Steel - Size/BCD: Direct mount - Recommended Group: EX1