Campagnolo's Record EPS V2 Power Unit is the reliable brain of Campy's electronic shifting. In order to keep your bike looking sleek, the mounting options allow it to sit inside your bike's frame. The 3-cell, 12-volt Lithium-ion battery delivers up to 1,200 miles on a single charge. It also houses the electronics necessary to deliver pinpoint shifting precision to the front and rear derailleur mechanisms (sold separately). For example, if you're cross-chained, the system immediately senses it and moves the front derailleur ever so slightly to avoid chain rub. Plus, the one-piece, ultrasonically-sealed unit is impervious to water or road vibration.