In reply to Newbuild100:
Over the years I've tried various mirrors on my drops.
Problem with most of them is that they vibrate on rough, and not so rough, roads, so not much use.
A few years ago I bought a B&M Star 80, with a short stubby stem which fits the end of the bars. No movement, no vibration and gives a good field of vision.
The model is shown on the B&M website as Cycle Star 80 version 903/2.
http://en.bumm.de/produkte/mehr/fahrrad-rueckspiegel/cycle-star-80.html
If it ever breaks, I'll def get another one.
Be aware that when I googled Star 80, most of them are shown with a long thin arm, so a different version. I think these would be more prone to vibration.