Reliable rearview radar with our most powerful and precise radar tracking technology detects vehicles approaching from behind and gives audible and visual alerts on your compatible Edge cycling computer, Garmin smartwatch or on the Varia app on your smartphone A bright tail light provides visibility from up to 2 km (1.24 miles) away to help you be more visible to motorists approaching from behind Get up to 24 hours of battery life in day flash mode and up to 30 hours in radar-only mode See visual alerts for small, medium and large vehicles approaching, and see the movement of a vehicle and its threat level — when riding with your compatible Edge cycling computer or the Varia app on your smartphone Show other cyclists or motorists that youre slowing or stopping with a brake light that displays a unique flash pattern Same-speed tracking means you can continue to stay alert to vehicles that are following behind at the same speed or attempting to pass (tracking may be unavailable at slower speeds or when radar is obstructed) Connect the Varia RearVue 820 rearview radar and tail light to the Varia app on your smartphone, select Garmin smartwatches or compatible Edge cycling computers for visual and audible alerts while you ride Ride with four different light patterns: day flash, night flash, solid mode and peloton mode; when riding with others, peloton mode preserves the eyes of others riding behind with a lower intensity flash; also, create your own custom light patterns in the Varia app on your smartphone Mounts onto your seat post and is compatible with the Varia seat rail mount kit (sold separately)