My first advice calls for a free fix first. Adjust your mirrors properly before deciding you need anything extra. Most people have their side mirrors adjusted to see behind them with significant overlap between them and the rearview mirror. If I am behind someone and can see the drivers face in 3 mirrors, they are not adjusted correctly. Start with this. I have never found a need for more than the three OEM mirrors on any vehicle I've driven. Okay, when I tow a trailer or have something blocking my rearview mirror, I bring the side mirrors in a little siice I do not have towing mirrors.
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