This is a set of mountain bike lights. They include two headlights and two taillights will batteries and USB cables for charging them up. They are really bright so that they can make sure that the rider is seen in the dark. The headlight has 5 modes, high, average, low, strobe and SOS so you can choose the one that is most appropriate for the conditions that you are in. The brightness is up to 700 lumens and can light up to 350 meters and can be used for up 7 hours. They are very durable so they resist scratches and bumps so stay in good condition and can cope with all weather conditions. They are designed to fit on a handlebar which is 20mm – 28mm in diameter.