Tested working Shimano Ultegra Di2 A-junction. These connect to the left and right shifters and then use a cable of your specific length to the rear (B-junction). The button is used to tune or reset the derailleurs, and the LED status indicators are tested and work properly. Check out my other compatible items for sale; all of my Di2 components are tuned and tested and updated to latest firmware versions using Shimano's professional computer interface. Ships in a padded envelope.