Shimano BT-DN320A Battery external such as Avid BB7

such as Avid BB7

The dual low-profile BOA Li2 dials offer precise micro-adjustments

and supports hookless rim compatibility for 28C and larger sizes (up to 73psi)

while the LED-compatible rear mounting area allows for easy integration of Lazer’s optional Universal LED light to improve visibility during low-light rides and commutes

And let's talk about that 44mm offset - that gives you unbeatable control and stability

Shimano BT-DN320A Battery external such as Avid BB7The Shimano BT DN320A Battery is designed to power Shimanos latest wireless Di2 shifting systems with smooth, reliable performance. Built to fit directly inside the new Wireless XTR Rear Derailleur, this compact battery is well protected from the elements and the roughest trails. With 310mAh capacity, it offers long lasting power so you can ride more and worry less about recharging. This battery stays securely tucked away inside the derailleur,