You've probably seen them around: Those fish-eye mirrors that drivers glue onto their side mirrors in hopes of solving their blind spot problem. Well, we've done the research and our verdict:
Steer clear of aftermarket stick-on mirrors because They're not safe or effective.

Here are 10 reasons why should never use auxiliary convex stick-on mirrors for blind spot coverage:

1. They distort your rear view
By nature, these mirrors are sharply convex mirrors that distort your view of what's behind you. This distorted view is what gives them the name "fish-eye mirrors". What makes things worse is that your eyes have to adjust on the fly between the fish eye view and the regular rear view reflected in your vehicle's original side mirror.

2. Only their outer edge is beneficial
As with every side mirror, the portion of the mirror that's most beneficial to expose what's in your blind spot is its outmost edge. The problem with these convex mirrors is that their fish-eye effect actually compresses items reflected in their outmost edge. So in a 3" stick-on convex mirror, only the outermost 1" is actually beneficial to show items in your blind spot and even then, such items appear distorted and compressed (squished).

3. They take up valuable mirror real-estate
The overall reflective area of your side mirror is designed specifically for your vehicle's dimensions. Rest assured that vehicle manufacturers go to great lengths to design a useful mirror surface. When you stick a fish-eye mirror on your side mirror, you're taking away valuable mirror real-estate and diminishing the usefulness of an essential safety tool in your vehicle. Picture this: On a 2006 Honda Accord, a circular 3-inch stick-on mirror reduces the usable reflective surface area of the Honda OEM side mirror by as much as 30%.

4. They look cheap and unattractive
Okay. This one goes without saying. Your vehicle is the second largest investment you make. So why cheapen its looks by applying these stick-on mirrors?

5. They do not absorb glare and reflected light
Again, most vehicles' side mirrors are designed to absorb reflected light and glare coming from vehicles behind you. Some provide an auto-dimming feature to eliminate the appropriate amount of glare reflected back at your eyes. Fish-eye stick-on mirrors do not have these same glare-absorption quality so you end squinting and covering your side mirror with your hand when driving at dusk or at night.

6. They're confusing to use
Stick-on mirrors are difficult to use reliably because you have to intently watch nested mirrors (the stick-on mirror stuck on top of your vehicle's side mirror) showing different objects moving at the same time. A fish-eye mirror on top of your regular mirror not only requires a lot of getting use-to, but it produces a very confusing optical effect, especially at highway speeds when you're trying to make quick decisions in rush hour traffic.

7. They do not comply with government safety regulations
The US Department of Transportation (DOT) and the National Highway Transportation Safety Administration (NHTSA) publish specific guidelines for the type of mirrors (unit magnification requirement) that automakers can use in passenger vehicles. Sharply convex auxiliary mirrors are generally not compliant with government safety regulations due to their variable unit magnification characteristic.

8. They're difficult to remove
The adhesive used by these mirrors is particularly strong. It is designed to withstand temperature extremes as well as moisture. The bad news is that these mirrors are particularly difficult to remove. They require special adhesive-removing chemical solvent that is costly and should be applied with care.

9. Leasing companies may charge you to remove them at lease end
So you decided to return your vehicle at lease end with your stick-on mirrors still attached to the vehicle? Better think again because some strict leasing companies have been know to charge their customers a fee to remove any aftermarket components (including such mirrors) in order to restore the vehicle to its factory condition (which is a requirement of your lease contract). So a $5 pair of stick-on mirrors could end up costing you $50 or more in lease-end charges. Is that really worth it?

10. Chemical required to remove them can be harmful to your vehicle's paint / clearcoat finish
So you decide to go the DYI route to remove these mirrors. The special adhesive-removing solvents required for the job are not exactly safe for us mere mortals, but they're also known to damage clearcoat finishes if you happen to drip it on the outside mirror housing or even worse on your vehicle's door panel. If you still want to go this route, be sure to read and follow the chemical's manufacturer instructions carefully.