Rearview radar with taillight senses approaching vehicles up to 153 yards (140 meters) from behind. Seamlessly pairs with your Edge bike computer and compatible smartphone and select Garmin wearables or radar display units. When used with your compatible smartphone, the app provides graphics as well as tone and vibration alerts to indicate approaching vehicles. When used with a compatible smartphone, the radar integrates with third-party apps such as Ride with GPS to overlay rearview radar alerts on your map. Daylight visibility up to 1 mile alerts drivers of your presence as quickly as possible. Compact vertical design easily mounts to most road bikes. Package includes: Housing (light not included). Note: Data are all manually measured; please allow 1-3 cm error. Due to different lighting and display settings, there may be some color variation. Please refer to the actual item received.