Shimano 7970 Dura-Ace Di2 Derailleur to Battery Internal Cable - Short Mount - 400mm. 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, and cobble stone roads. 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. Dura-Ace Di2 requires 2 cables: a handlebar cable set to connect the shifters to a battery indicator junction box, and the other to connect the handlebar cable to the battery and derailleurs. This cable is for connecting the battery to derailleurs internally. Internal cable sets are for bikes specifically designed for Di2 to ensure clean lines and minimal rider interference. This cable set uses a frame specific short battery mount for discreet installation with a 400 mm battery to bottom bracket junction lead.