Shimano Di2 Batteries. Must purchase battery, charger, and power cable to complete the system.

• All Di2 components on the bicycle require the same firmware version. Using Di2 components with different firmware versions may cause malfunction. Update component firmware from http://e-tubeproject.shimano.com/
• Compatible with thinner, next generation electric SD300 wires. 
• Features three SD300 wire ports
• Shared fixing method with BT-DN110
• Built-in type, intended to be stored in the bicycle's seatpost.