Varia™ RTL515 rearview radar provides visual and audible alerts for vehicles approaching from behind up to 140 metres away.

It features multiple modes, including peloton mode, which provides a low-intensity flash that is kind to other cyclists’ eyes when riding in a group.
 
Alert motorists to your presence as soon as possible with daylight visibility up to 1 mile.
 
Pair and control the built-in camera with your Edge® bike computer or compatible smartphone as well as selected Garmin wearables.
 
Easily mount this sleek, compact device on the seatpost of almost any bicycle. The vertical design allows for leg clearance and a perfectly comfortable ride.

Get up to 16 hours of battery life in day flash mode and up to 6 hours in solid mode.
 
See more details here
https://www.garmin.com/en-GB/p/698001/pn/010-02377-00
 
PART NUMBER010-02377-00