The Shimano EW-SD300 is a Di2 electronic wire designed for connecting Shimano’s 12-speed electronic shifting components, including road (Dura-Ace R9200, Ultegra R8100, 105 R7100), gravel, triathlon, and mountain bikes (plus EP8/EP800 e-bike systems). It is part of Shimano’s second generation E-Tube wires, featuring a more compact and lightweight design compared to older models like the EW-SD50. The wire diameter is approximately 2.4mm with a plug diameter of 3.45mm, which allows for easier internal routing and reduced weight on the bike frame. The EW-SD300 wires come in various lengths from 150mm up to 1600mm, accommodating different frame sizes and routing needs.

These wires carry both power and data and require the TL-EW300 cable plug tool for proper connector assembly. They are not backward compatible with pre-12-speed Di2 systems without an adapter (EW-AD305). This wire is suited for cyclists upgrading to or maintaining current 12-speed Di2 systems, offering reliable electrical connection between derailleurs and battery while enabling compatibility with future system expansions. Its compact design enhances installation flexibility and frame integration, making it ideal for modern road and e-bike setups.