well i have the top one adjusted as follows.
lean against glass and angle top mirror to where it would be and then the bottom i have where my blind spot is and a little angled up so i can see the lanes next to me and farther back so i get a wide range of vision.
heres pic of my old truck and how i set my mirrors.
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so at a quick glance you not only see your blind spot, you can change lanes with ease and still see everything. Once a car left the top mirror they showed up in the bottom one either front or back. I never had a blind spot with them set that way.
