The latest revision of Sram`s X-Sync II chainring for use with Eagle 12 speed chains The longer, positive-rake tooth shape has been designed to work perfectly with the new Eagle chain to increase chain retention and overall pedaling efficiency, while decreasing friction, noise and wear Improved design through study of thousands of X-Sync chainrings wear characteristics Direct Mount 36T Alloy GXP/BB30 Boost Lunar-Grey 12sp Narrow/Wide 3mm