My wife has been through a ton of barend mirrors ever since she broke her neck and had to get spinal fusion surgery (limited head rotational range-of-motion makes mirrors a mandatory accessory for her...which she uses in addition to the Garmin Varia rear-facing radar).

After trying the Mirrycle, the Sprintech, two different Hafny models, and the Berthoud, the one she found best -- based on clarity of optics, ease of adjustment, and not needing to be constantly readjusted (i.e., staying in one position, not getting jostled around just from the act of cycling) -- is the ~2.25" diameter Hafney HD Convex Blue Glass Mirror with the Automotive Grade Glass. https://www.amazon.com/gp/product/B07WMMQJFW/