All the threads that the fittings screw into need to be cleaned with a tap to avoid the risk of stripping them on the first tightening. Also be careful when tightening because the metal is as cheap as it gets.
But the worst thing about these mirrors is that they are not like vehicle mirrors; they are plain, like household ones, with the result that the field of view you get, especially on something so narrow as these, is almost useless. Unfortunately this happens with cheap mirrors, but that does not make them any less almost useless. Maybe the situation can be saved if someone puts a wide-angle adhesive film on them so they can essentially be used as a base.
It is also a shame that their arm is not hollow in the middle. It would look better and create less wind resistance.
In short, if they had proper glass they would be a fair purchase despite the other flaws, which, if you are a careful enough handyman, you can fix. With glass like this, no.