Years ago, I had a Toyota 4WD p/u that had the sizeable (4x6 ?) outside mirrors. This was the early 80s and the right-hand mirrors were still the "flat" style so I put a 2" round convex mirror in the upper right-hand of the passenger mirror and a 1.5" round mirror for the driver's side mirror, also in the upper right-hand corner. As I had a shell on the bed, that corner was pretty much a "dead" area and that round convex mirror gave me enough detail to see colors & shapes and make me take a closer look.