Shimano Ultegra R8050 Series Dealer's Manual page 117

CONNECTION OF ELECTRIC WIRES
Connection of junction B
Connecting to FD-R8050
Attach the plug cover to the electric wire.
Connect the electric wire to the front derailleur together with the plug cover.
(A)
4
Connecting to other parts
Connect the electric wires to the rear derailleur and the battery mount.
Rear derailleur
(A)
4
(B)
Battery mount
(A)
117
(A)
Plug cover
(B)
Electric wire
(A)
Shimano original tool TL-EW02