Shimano SM-JC41 Junction Box, Junction B Shimano SM-JC junction box, junction B, for internal frame cable routing SD50 ports: 4 Compatible with Dura Ace 9070, Ultegra 6870 / 6770, XTR 9050, XT 8050, Alfine Di2, and Nexus Di2 systems. Not compatible with Dura Ace 7970 Di2 systems. Product code: ISMJC41 EAN: 4524667827467