Shimano SM-BMR1 Base B Unit (M4 x 16) [Y7F398050]
It is compatible with Internal/External type short Di2 batteries.
Shimano EW-WU111 E-TUBE Wireless Unit (D-FLY 2-Port Junction) [IEWWU111B]
Allows for use of ANT+ and Bluetooth LE connections (including Shimano software and E-TUBE Project). The Shimano EW-WU111 is an inline connector that enables the use of ANT+ and Bluetooth LE accessories.