I'm sure this light has many different uses, but we use them on the back of our bikes. By the time my wife and I get home form work, it's usually dark or getting dark so we have these attached to the back of our bikes as e normal ride almost every night for exercise. The light is bright, works great-you can be seen for quite a long distance, and the batteries seem to last forever.

I bought two of these and wear one on each arm when I run at night. They are very visible, work well, and last a fairly long time on one pair of batteries. Although I always try to avoid major thoroughfares, these lights are especially helpful for making you standout on darker side streets.