historic broken neck and limited lateral movement, I'd echo what others have said, they are a superb feature on a bike and a good one is no different to using wing and rear view mirrors in a car. My shoulder check now is simply an additional indication to anyone following me that I'm imminently going to move out/turn.
A question before you plump for one type: what type of bars? different mirrors are suited to different types. nearly 20 years of necessity experience has given me the following few that are streets ahead of their rivals. Invariably they're Zefal. I seriously cannot recomment them highly enough.
for flat straight bars you can't beat a Zefal Dooback,
for flat, raked back up to full moustache type bars, either the zefal spy that is in Potsy's pic or a zefal spin are excellent,
for drops the best is the sprintech bar end mirror but either the spin (currently using one on my drops cos my sprintech got nicked) or the spy work well too - I have spin and spy and have tried them both, by preference I have the spin fitted. This also wins because it sits out to the side of the bar and doesn'y catch a view of my full pannniers now I've made a more audaxy vibe to my rpad bike
The spy is uesful as it can sit around the hoods with a little bit of zip tie fettling if your bars are tilted a bit upwards and the drop ends fall short of the tops and get obscured.
The key is to get one that plugs directly into the bar end, or like the spy clamps properly onto it and has no sort of arm to introduce vibration.
No offence to numbnuts but the few Blackburn mirror's I've tried over the years has been very poor, invariably unable to give you a steady image the way zefals and sprintech do. cateyes too wobble, I don't know what it is with them, but the arm, fitment to the bike or where used the ball and socket joints just arent as snug or durable as commensurate parts on the Zefal's and Sprintech.
