Shimano di2 ew90 junction a box 3 portthe removal of traditional mechanical cables in favour of electrical wires not only eliminates poor shifting caused by contaminates corrosion and stretching but provides effortless gear shifts features this junction a is required to connect the shifters via e tube wires to the downtube junction wire 3 port design one for downtube wire to bottom bracket junction two for shifter connection battery level indicator feature e tube ew sd50 wires not include