I used these for a while. Fold up feature is very nice, quality is good. Still use them on other bike but went back to stock mirrors because the fairing will have an unfinished look on a firebolt. Some guys have plugged the mirror mount holes with turn signals on a FB but a non issue on others. https://www.amazon.com/gp/product/B0...ilpage_o04_s00
I use very cheap ones. Much like levers, I consider them a disposable part of the bike. No sense in spending $200 even for a 'lifetime replacement' because disposable or not I'll never need 10 sets (+shipping).
For me, the most important thing is that they mount with an aluminum expansion sleeve and not plastic or rubber. If the mirrors you like have plastic, you can get the aluminum sleeve at most True Value Ace hardware stores.
Secondly, they need to be convex. Flat 3" mirrors do nothing.
Thirdly, I like if they have a detent so if I pull them in I can just knock them back into place without re-adjusting my view.