I had to replace my wife's rear derailleur after partially running over her bike with our car after a bike ride. She had an earlier model of the Di2 rear derailleur, but this newer version worked perfectly. It is super easy to install, looks great and shifts beautifully. True plug and play replacement.
Matches the color of today's matte black finish bikes . Seems to shift a bit quieter when shifting to different gears compared to the old . The only problem I had is that you have to make sure the derailleur is in a slight angle back when mounting on the hanger or else you won't able to take the rear wheel off the bike .