It is nice to have your mirror attached to your bike. You never leave home without it. The problem is that you get a very narrow field of view using a reasonably sized flat mirror at arms length. We get the correct angle of view by making the Bar End Mirror convex. That is where you get the vehicles may be closer than they appear effect .
Flat mirrors give a life size view, just like stopping, turning around and looking.
Given a straight road, you can see another bicycle two miles behind you with any of our other mirrors. .