I think I had my 1st cycling mirror 15 or 20 years ago. It stuck on to the helmet or glasses. Whenever I took my helmet off or my glasses off I had to readjust it. It broke. Don't recall how well it worked. Must have sucked because after it broke I went 15 or 20 years without one.
So I found one that fell off a bike. Kinda nifty. Fits onto the bars, drops, and is secured by a velcro strap. Incredible adjustablility. Easy to swap to different bikes. Thought I was lucky.
First major use was my ride to Dallas Center. I placed it on the tandem. Major issue was that I never used it. guess that it was so new that I forgot that it was there. It took some time to start using it.
Next issue is the "objects apear smaller." I am talking about "objects appear so damn small that you will not see them until they are right up your ass" smaller. Seriously, even semi-trucks are invisible until they are right on me. Piece of shit.
The one and only advantage---get ready---night riding. The mirror does a good job reporting the presence of car lights behind me. That is its only value.
So if you know anyone who lost a mirror on the kybo bridge in Water Works park, let them know I found it.