Shimano Dura-Ace Di2 RD-R9150 Shadow Rear Derailleur 11-speed black

The new Dura Ace from Shimano is answers the question of many pros and ambitious amateurs as to whether and how the current, immensely high level of performance could be further increased. Each individual Dura Ace R9100 component is designed to work as efficiently as possible with all other components of the system. This shows the core of Shimano's component-developed-as-a-system philosophy particularly clearly. The result is called SYSTEM SUPREMACY - the superiority of the system over the sum of the individual parts.The new Dura Ace rear derailleur comes with a fundamental design change, the Shimano RD architecture (from the MTB sector) served as a basic building block. This low-profile design provides a slim appearance while improving the ability to withstand damage from falls.