Shimano EW-SD50 Di2 750mm Etube Wire 

• Ultegra Di2 wires utilize Shimano's e-tube technology; e-tube is a two-prong system and is NOT cross compatible with Dura-Ace 7970 Di2 wiring
• All e-tube wires may be used for internal or external applications
• Frame grommets for E-tube internal-wiring compatible frames are sold separately, see Shimano Frame Grommet Kit Electronic Shifter Extra Parts