Campagnolo's Athena EPS Rear Derailleur uses an advanced-parallelogram design that assures quick, precise shifting, while high-power servo motors make it effortless. The near-instant response is as impressive as being able to shift all 11 gears with a mere button hold. No matter what gear, the position sensor automatically adjusts for perfect alignment on every shift. And, in the unlikely event of a system malfunction, the manual release allows you to move the rear derailleur to your desired gear to get you home. Plus, the aluminum and carbon construction keeps weight low and boosts strength and the pulleys are made from a special rubber for whisper quiet drivetrain action.