From a quick Google it looks like they are just … small mirrors … that most people can’t see anything with … and possibly illegal in some States in the US because they aren’t big enough.
Since you don’t need to have mirrors here - then I guess they are legal - but then if you are going to fit smaller mirrors just to look good but serve no purpose - then why not lose them altogether?
Just googled myself. I lead a lot of ride outs and would be sooo lost without my mirrors.Bikes definately seem to look a bit cooler but cool over my life… mirrors please!