Garmin Varia RTL515 Radar Tail Light - This rearview radar with tail light pairs with your Edge bike computer or compatible smartphone to alert you of vehicles approaching from behind. Features Maximum Awareness - Varia RTL515 rearview radar provides visual and audible alerts for vehicles approaching from behind up to 153 yards (140 meters) away. Multiple Pairing Options - This radar works seamlessly with your Edge bike computer or compatible smartphone as well as select Garmin wearables or the optional radar display unit. Works With The Varia App - This smartphone app helps you increase your awareness by providing graphics plus tone and vibration alerts that indicate the position and speed of approaching cars. Third Party App Compatible - When used with a compatible smartphone, Varia radar integrates with your favorite apps, such as Ride with GPS, to overlay your maps with rearview radar alerts. Superior Visibility - Alert motorists to your presence as soon as possible with daylight visibility up to 1 mile. Compact Design - Easily mount this sleek, compact device on the seatpost of almost any road-use bicycle. The vertical design allows for better leg clearance and a perfectly comfortable ride. Peloton Mode - Varia RTL515 features multiple modes, including peloton mode, which provides a low-intensity flash that is kind to other cyclists’ eyes when riding in a group. Battery Life - Time spent charging is not as good as time spent riding. Get up to 16 hours of battery life in day flash mode and up to 6 hours in solid mode.