The downsides of most lights is that the batteries can die without warning, or that they can be bulky or awkward to carry. The Million Mile Light is a unique way to look at the problem of night time safety. As a bit of a closet conservationist, one of my favorite features of this light is that it is powered by kinetic energy. That means you will never run out of batteries, and the 4 LEDs should last a significant amount of time. There are batteries within these, that apparently your movement causes them to change position and power the lights. As with any magnet, be sure to keep them a safe distance from your electronics. The four LEDs on each housing flash in a pattern that is very noticeable.
They can be ordered with either white or red LEDs. Due to the rapid flashing pattern, I would not recommend trying to use the white one to see by. These are definitely to be used as visibility, not sight devices. Each housing has a clip on the back that can attach to a belt, or your pants/shorts. They sell a simple belt with a cool reflective patch featuring a lightning bolt, or you could attach them to a gear belt you may already own.You can get one of these belts free for every two lights you order ($30 each). One tip I will dispense if using their belt is to make it fairly snug, or it may start to rotate. Once figured that out, it was quite comfortable and I nearly forgot I was wearing it.
As someone who runs at all hours of the day, safety is an important issue. I have been involved in near misses several times and definitely dress to be noticed when I go run. These lights definitely get the job done, with no drawbacks that I noticed.