This is one of those items that seems a little too "techy and gimicky" at first glance, but once you ride with it, you will be converted. Quick and easy install. Very visible light with multiple flash modes. When sync'd to the Garmin or Wahoo compatible computers, you get a visible and audible warning from the computer of cars approaching from the rear. It will "see" them long before you hear them. Multiple cars? It will show how many, and even how quickly they are closing to you. I'd rather leave home without my helmet than my Garmin Varia RTL515.