The Alfine 8 speed Di2 specification internal gear hub runs on needle bearings for increased durability and high drive efficiency. The Shimano Alfine S7051-8 hub offers a wide 307% gear range actuated by Shimano Di2 electronic shifting and an improved internal structure for better gear engagement. It is approved for E-Bike and non E-Bike use and is available in black and silver. Technology Power Modulator As for the front roller brake, the braking Power Modulator system is built in the hub side to ease sudden lever power input for easy and stable braking control. The braking system is especially user-friendly for beginners. Centre Lock The Centre Lock system makes an easy rotor installation possible with spline mount and a lock ring. The lock ring mounting system reduces the total working hours by shortening the amount of time of both installation and de-installation. In addition, the secure fixing by the spline mount enhances precision and rigidity while improving braking efficiency. Features Top normal internal structure for improved tolerance when shifting while riding under load Labyrinth seals improve sealing performance extending service life Alfine hubs use pedal power to aid down-shifting resulting in fast and accurate shifts with an exceptionally light feel Double roller clutch engagement also gives a smoother quieter shift Shimano's precise manufacturing abilities have enabled them to construct the Alfine internal hub to be there most efficient yet Centre-Lock disc rotor compatible 135mm O.L.D. spacing