I've tried many of the mirrors sold over the past 20 years.

Bar mirrors always seem to get in the way, and they don't transfer easily from one bike to another. Also, they usually provide an inferior rear view to helmet mirrors. I wish there was one that worked well.

I've used a Cycleaware Reflex helmet mirror for about eight years now. It's not perfect but it's the best I've found. I got my last one from Amazon for about $13.

http://www.amazon.com/Cycleaware-Ref...leaware+reflex