The Athena rear derailleur has the same geometry as the top of the range 11 speed models, and absolute precision is the result. The outer plate wraps around the upper and lower bodies in aluminium, eliminating any possible play and making the overall structure of the rear derailleur extremely stiff. The result is fast and precise shifting in all the gears. The pulleys are specially designed to reduce vibrations and make the drivetrain perfectly quiet. upper to lower pulley axle: 55 mm aluminium outer plate parallelogram with 11s geometry die cast aluminium upper body lightened special rubber pulleys.