What Is the Shimano EW90-A Di2 Junction Box For?

The Shimano EW90-A is a 3-port Di2 cockpit junction box for older-generation Di2 systems including Dura-Ace 9070 and Ultegra 6870, mounting at the stem or handlebar to serve as the central wiring hub connecting derailleurs and battery via EW-SD50 E-Tube wires. The mode button built into the EW90-A allows Di2 settings adjustment and component syncing without a computer, and the display port enables connection to a cycling computer for real-time gear position display. Three ports accommodate front derailleur, rear derailleur, and an optional satellite shifter or additional junction.

Compatible with Shimano Di2 systems using EW-SD50 wiring -- Dura-Ace 9070, Ultegra 6870, and compatible older Di2 groupsets. Not compatible with current-generation 12-speed Di2 systems using EW-SD300 wiring, which do not require a separate junction box.