Shimano jc41 e tube di2 internal junction box theshimano di2 sm jc41 internal junction boxis the grand central station of the e tube di2 system all of the component and battery wires meet here before running out to their respective components all of the wires that connect to the junction box use the same connector to make assembly that much easier featuressm jc41 cable junction for internal wire routing junction is required for connection of rear mech front mech battery and cable to batt