シマノ BT-DN320 バッテリー

Shimano Di2 internal seatpost / frame battery — the power source for electronic shifting. Plug-compatible with the E-Tube wire harness standard; mounted internally so nothing sits on the outside of the frame. Typical lifespan is several years of daily use before it won't hold a charge through a training ride. This is the Shimano BT-DN320 Battery.