Brand new Dura-Ace 12-speed Rear Derailleur from Shimano.

The Shimano Dura-Ace Di2 12-speed rear derailleur is the centerpiece of Shimano’s top-of-the-line Dura-Ace Di2 road bike group, offering semi-wireless and fully wired shifting. Constructed primarily of aluminum and carbon, it is approximately 50 grams lighter than the Ultegra model. The RD-R9250, in its disc brake version, communicates wirelessly with the shift/brake lever via a built-in radio chip, offering more functionality than a traditional rear derailleur. Rim brake versions with cable connection to STI are responsible for coupling the components.

The rear derailleur is connected to the battery via a cable, from which there is also a cable to the front derailleur and, if applicable, to his STI. It has a charging port and the circuit can be easily charged with the appropriate charging cable. In racing and training use, the RD-R9250 impresses with extremely fast switching speeds that clearly exceed those of its predecessor. Its flat shadow design reduces the risk of snagging and optimizes shifting.

With a total capacity of 37 teeth, you can switch between 12-speed cassettes with maximum sprockets from 28 to 34 teeth. 54-40 teeth provide variability and optimum conversion for all driving situations.

Specifications:

Brand new
Di2 wireless chip with low interference, fast processing, and low power consumption
Shifting speed is incredibly fast: 58% faster than the RD-R9150
E-Tube Project firmware updates
Derailleur Pulleys: 11-tooth
Outer Cage Material: carbon (CFRP)
Inner Cage Material: carbon (CFRP)
Compatible with HG 12-speed chains
Linked to battery via cable
Great Shimano quality