The Shimano BT-DN300 Built-In Type Di2 Battery is the power source for Shimano's 12-speed Di2 derailleurs (and shifters in fully-wired configurations). While remaining the same size as its predecessor, the DN300 now has 3 connection ports to enable simple wiring options. Its thin, sleek profile allows the battery to fit in seatposts or frames for a clean look. Features: Compatible with thinner next generation electric wire SD300 and systems after R9250/R8150 series 3 SD300 ports Shared fixing method with BT-DN110 Waterproof design Specifications: Battery Chemistry: Li-Ion Rated Voltage: 7.4V Rated Capacity: 0.5 Ah / 3.7Wh Ports: SD300 x3 Weight: 52g