To ensure that the signal goes from the shifter to the derailleurs the reliability of the electric cable has been proven by repeated field tests in various riding conditions including extreme temperatures rain mud & cobble stone roads The removal of traditional mechanical cables in favour of electrical wires not only eliminates poor shifting caused by contaminates corrosion & stretching but provides effortless gear shifts Dura-Ace Di 2 requires 2 cables: a handlebar cable set to connect the shifters to a battery indicator junction box & the other to connect the handlebar cable to the battery & derailleurs This battery to derailleur cable set uses internal down tube routing with external front & rear mech routing in conjunction with a long battery mount for neat fitment on bottle cage bosses Reliable & secure water resistant connectors