These light are very good.
+ It is easy to attach to the handlebar (or frame).
+ you will be noticed when it is on, but
+ it is very inconspicuous when they are off (so they don't get stolen right away).
+ batteries are easy to change and
+ they will last a long time (I did not need to change them yet).
+/- you can use it as a headlight to see where you are going, but it is not really made for that.
One minor thing I don't like is
- you need to press 4 times for every cycle on-off, and you need to press hard. The button is a bit spungy because it has a rod of the silicone that goes all the way in. That makes it a bit hard to press with gloves on.