Sram X-SYNC 2 technology optimized for 1x12 Eagle drivetrains X-SYNC 2 design increases chain retention and wear life, and reduces friction and noise Also compatible with Sram 11 speed drivetrains Optimized for use without a chain guide CNC machined 104mm 4-bolt 38T Black 12sp Narrow/WideUPC/EAN/GTIN: 710845795565