Only protective shellRearview radar with tail light provides awareness of vehicles approaching from behind up to 153 yards (140 meters) awayPairs seamlessly with your Edge bike computer and compatible smartphone as well as select Garmin wearables or the radar display unitWhen used with your compatible smartphone, the app provides graphics plus tone and vibration alerts that indicate approaching carsWhen used with a compatible smartphone, radar integrates with third-party apps such as Ride with GPS to overlay your maps with rearview radar alertsDaylight visibility up to 1 mile alerts motorists to your presence as soon as possibleCompact vertical design mounts easily to most road-use bicycles Note: The data are all measured manually, please allow 1-3cm error, due to the difference in light and display, there will be a certain color difference, the actual object received shall prevail.