Shimano di2 junction a sm ew90 b 5 port the 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 this junction a is required to connect the shifters via e tube wires to the down tube junction wire 5 port design one for down tube wire to bottom bracket junction four for shifter connection ideally suited for tttriathlon with multiple shifter positions