A suitable choice for anyone repairing, replacing or building a compatible SD50 Di2 system with internal routing and four connection points.
The SM-JC41 is a compact Junction B for electronic shifting systems that use dedicated SD50 electric wires. It provides four SD50 ports, giving you a central connection point for wiring between the front and rear of the bike, cockpit components and battery where the system layout requires it.
Designed for internal wire routing, the unit sits inside the frame or component area to keep the wiring tidy and out of sight. Its small 30.5 x 14.5 x 8 mm footprint suits discreet installations, although you should check the available space because connected E-Tube wires extend beyond the junction itself.
At just 4.1 g, it adds very little weight. This is a practical replacement or build component for compatible 10-, 11- or 12-speed Di2 arrangements using SD50 wiring, including installations where extra ports are useful around a time-trial or triathlon cockpit. It is an SD50 component only: the specification lists no SD300 ports and no master-unit or E-TUBE PROJECT firmware-update function.
Four SD50 ports
Connects up to four compatible SD50 E-Tube wires in one compact junction.
Internal installation
Designed to sit inside the frame or component area for a cleaner, less exposed wiring layout.
Compact footprint
Measures 30.5 x 14.5 x 8 mm, making it useful where installation space is limited.
Very light
At 4.1 g, it adds minimal weight to the electronic shifting system.
Useful for cockpit wiring
The four-port layout can help connect multiple front-end shifting controls in suitable time-trial or triathlon configurations.
SD50 system compatibility
Built specifically for SD50 wiring; it has no SD300 ports, so confirm your system standard before ordering.
Straightforward replacement
A practical Junction B option when an existing four-port internal junction needs replacing.
General
Connectivity
Dimensions & weight
System functions
SHIMANO Di2
A SHIMANO electronic shifting system using dedicated junctions and electric wires to connect compatible components.
SD50 internal wire routing
The built-in junction is designed to sit inside the frame or component area, keeping SD50 wiring organised and out of sight.
