Shimano EW-SD50 Di2 External B Junction Box

This is the Shimano Ultegra Di2 External Junction Box for connecting the two derailleurs, battery, and cockpit controls in a Shimano Di2 electronic shifting system. This junction works with all Di2 with e-tube wired system components as long as firmware is updated to same version between all the connected components. Features: Mounts underneath the bottom bracket shell Frame Junction Box connects via SD50 E-tube wires to four different points: front derailleur, rear deailleur, cockpit junction box and battery mount Use Di2 system checker to update component firmware from http://e-tubeproject.shimano.com/ All Di2 components on the bicycle require the same firmware version. Using Di2 components with different firmware versions may cause malfunctions