The removal of traditional mechanical cables in favour of electrical wires not only eliminates poor shifting caused by contaminates, corrosion and stretching, but gives effortless gear shiftsUltegra Di2 uses a fully removable individual cable system from the battery indicator junction box enabling fine tuning with the correct cable length to each component for easy and tidy fitmentEW-SD50 wires are required to connect the junction (either SM-JC40 external or SM-JC41 internal to the rear mech, front mech, battery and to the handlebar battery indicator junction boxEW-SD50 individual wires are available in varying lengths, there is no need (or facility) to cut these cablesReliable and secure water resistant connectors.