What's the name of the small round mirror added to the rearview mirror?

A mirror with a small circle on the rearview mirror is called a rear-view small round mirror, also known as a blind spot mirror, a reversing small round mirror, a wide-angle mirror, and an automobile rearview mirror auxiliary mirror. There is no standard title.

The rear-view small round mirror is an ideal auxiliary product to ensure driving safety, increase the observation angle of drivers and change lanes when overtaking. Small round mirror is also an ideal auxiliary tool for reversing, generally installed under the left and right rearview mirrors. On a vehicle equipped with a rear-view small round mirror, the driver can see the side of the car body and the rear wheel, which is also the biggest use of the rear-view small round mirror. It should be noted that the small round mirror in the rear view can't see the blind spot when changing lanes and turning, especially at night.

Another disadvantage of the small round mirror is that it is deformed and the distance is severely distorted. In addition, sticking a small round mirror on a good lens will seem a bit awkward. The advantage is that it is cheap.