Like Marvinsgarden, I rode BMW motorcycles for years. Before them, I rode thousands of miles on English bicycles. All those mirrors had flat glass and stems long enough to get them out past my arm and up somewhere near eye level.
I didn't find anything like that for my Radrunner, so I tried an end mirror. On my first ride, I heard a car close behind me. I studied my mirror and couldn't see it. When we came to a straight stretch, it passed. Its gray paint was about the same shade as the pavement, and the convex mirror made its image six times smaller. I rode straight home and removed that hazardous mirror.
I ordered one that was supposed to be flat. It was convex, making images three times smaller. What's more, I couldn't see past my arm. I mounted it upside down on the right and bought a right-hand mirror to mount upside down on the left. I really didn't feel safe.
Then I found a flat mirror with an 11.5" stem: the Sunlite HD II. Friction keeps the stem from rotating in the clamp, but I could swing the mirror inboard if necessary for storage. Before removing the right convex mirror, I took photos of a car with a high-contrast paint color only 100 feet behind me, under midday light.