Shimano Dura-Ace 7970 Di2 EW-7975 Internal Wiring Kit With BB Inner CoverShimano Dura Ace 7970 Di2 EW 7975 Internal Wiring Kit 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,