Product details:

Shimano's EW-WU111 Wireless Unit allows wireless communication with Garmin and other compatible cycling computers. In addition, the EW-WU111 lets you program your DI2 preferences on a Bluetooth LE smartphone or tablet with Shimano's DI2 app. At just 38 millimeters long and only a little wider than brake housing, the unit is unobtrusive. The transmitter clips onto brake housing for clean installation. Use in conjunction with external battery mount BM-DN100 or seat post battery BT-DN110. Requires extra cable (not included) for in-line installation.

• E-tube Di2 D-FLY inline data transmission wireless unit
• Allows information to be sent wirelessly via ANT+ private network to compatible cycle computers
• Information can be displayed about gear position and Di2 battery level
• Clean integration and installation with E-tube system
• Internal chip enables system wireless functionality of Bluetooth components
• Plug tool required for inserting and removing E-tube Di2 wires
• To be used in conjunction with BT-DN110 or SM-BTR1
• Average weight 5 grams