Shimano Di2 Batteries. Must purchase battery, charger, and power cable to complete the system. FEATURES : All Di2 components on the bicycle require the same firmware version. Using Di2 components with different firmware versions may cause malfunctions Use Di2 system checker to update component firmware from http://e-tubeproject.shimano.com/ The Shimano Di2 Internal Battery is designed to fit with internal mounts, offering a hidden solution for Shimano Di2 drivetrains Li-Ion battery power Shifter/Derailleur Compatibility: E-Tube , Shimano Ultegra Di2 , Dura-Ace 7970 Di2 , Dura-Ace 9070 Di2