Stay aware of approaching cars with the Varia RVR315 rearview radar. It pairs with your Edge bike computer or compatible smartphone to alert you of vehicles approaching from behind up to 153 yards (140 meters) away. When used with your compatible smartphone, the Varia app uses bold graphics—plus tone and vibration alerts—to indicate the position and speed of approaching vehicles.Reliable rearview radar lets you ride like you know what’s coming. Pair it with your compatible Garmin device, your phone, or both. Don’t have an Edge® or other compatible device yet? No problem. The Varia™ app has you covered.It’s small, it’s easy to mount, and it works with just about any bike. Get more life out of your radar with up to 7 hours of battery life.