Electronic goes affordable, and now to 11 speeds.
The Di2 FD-6870 Front Derailleur is once again the beneficiary of trickle down from the flagship Dura-Ace electronic design, offering amazingly smooth gear changes for an 11-speed drivetrain thanks to its microchip communication link with the gear levers. The derailleur's programmed cage motion does away with chain drop, and a self-trimming feature automatically adjusts the derailleur's position relative to the rear cog being engaged, making chain rub a thing of the past as well.
Limit screws are still set manually, so once properly set-up for your bike, the FD-6870 shifts perfectly every time. Slightly larger internals add a few extra grams compared to the 9070 model while significantly lowering the price.
Note: The FD-6870 is compatible with Dura-Ace Di2 9070 11 speed components.