How to distinguish the real capacity of U disk?

How to distinguish the true and false capacity of U disk? At present, because there are too many manufacturers of U disks and the competition is too vicious, some manufacturers have started to make U disks with fake capacity, and the chips used are also called upgrade chips. When you right-click on such a product when you connect to the computer, the properties are normal, such as 2GB, but the actual capacity that can actually be used may be only a few hundred MB or even a few MB; the way to distinguish is to copy a U disk full and pull out Switch to another computer and connect it to another computer to see if the files you just copied are fully usable. This is the most direct way to test whether the U disk has the nominal capacity.