Shimano Zee M640 Rear Derailleur
The Shimano 10 speed Zee Rear Derailleur features Shadow Plus technology that significantly reduces chain noise and offers a more stable drivetrain.
I have been using this derailleur for a couple months. Before I used a clutch derailleur, I did not believe all the hype of how good the clutch derailleurs worked. Well, they are right, it makes the drivetrain much quieter and smoother. The clutch on/off lever makes taking the rear wheel off much easier as well. Overall a great product this far.