Shimano Di2 4 Port Junction EW-JC304

Frame Junction Box connects via SD50 E-tube wires to four different points: front derailleur, rear derailleur, cockpit junction box and battery mount. The Shimano 4 Port Junction EW-JC304 is used inside the bicycle frame to connect four EW-SD300 E-Tube wires to each other. Connects 12-speed Di2 Rim Brake levers (8150 & 9250) to the EW-SD300 Di2 E-Tube Wire that connects to the battery. All Di2 components on the bicycle require the same firmware version. Using Di2 components with different firmware versions may cause malfunctions.