The Joule 3 dynamo hub 20” rim set lets you generate electricity to power your lights or charge devices on your bike while riding. The Joule 3, winner of a 2012 Eurobike Award, is one of the lightest, most efficient bicycle dynamo hubs on the market, which means more power generated at a given speed. The patented magnet configuration yields barely noticeable drag while a polished, laser etched, and precision-machined flange pattern present high performance in a beautiful, small package.