This shimano ultegra 6800 11 speed rear hub is a cold forged aluminium hub for serious road cyclists with improved sealing performance through the use of low friction labyrinth and contact seals and an internal grease sleeve using a special boron nitride machining process that has been applied to the cones to make them rotate super smooth the ultegra 6800 rear hub is a light and hardwearing bit of kit available in 32 and 36 hole