If I remember correctly, there is a verticle line in the mirror to show where the convex distortion begins. I lean toward mirror when making lane change to review full field of undistorted view. You can do same with Euro mirror.

The Euro mirrors are superior at showing objects in blind spot. I think they don't meet NHTSA standards 😏

__________________
-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991