Shimano Nexus Hub The internal hub houses the gears, bearings and brakes; the parts that when left exposed lead to mechanical failure, dropped chains, poor shifting, constant adjusting, maintenance and mess. Shimano put all that technical stuff inside their internal hub to protect it so that you can enjoy your bike without worry or problems. This very advanced system also gives you the most precise and convenient shifting available. Now you can have the pleasure of multi-gear Electra ride with ease comfort and seamless gear changes even standing still. Pretty smart, huh?