Originally Posted by
canklecat
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Positioning is critical to making a helmet or glasses mirror easy to use. If it's too far inboard the view will be blocked by your own head and you'll need to turn your head too much to see anything. If it's too far outboard you'll feel some eye strain from looking so far over. When it's within an ideal position range it's more intuitive, and you can often see movement behind you without actually looking at the mirror.
+1 I use a different mirror/system (see last post) but yes, positioning is key. I not only look at the inboard vs outboard but also the height to bring the mirror entirely into the upper corner of my glasses view (and select glasses with a "square" outboard top corner). I do need to move my head, but not much and being able to see behind with 20-20 is worth a lot. (I also do not wear progressive lenses but stick with hard bifocals because the vision at that distant corner on progressives is far from 20-20.)
Ben