I really like the idea of having a mirror when biking since I do a lot of biking on the road and we all know how bad drivers are when it comes to cyclists. The only thing I don't like about this product is that the mirror is so tiny that it is hard to see the cars coming up on you so it takes your eyes off the road for too long.
The mirrow worked great. I just finished a 130 mile ride over smooth and rough roads, and the mirror stated put. I vibrated, due to the rough roads, but It allowed me to see traffic behind me. I recommend it.