Most of these don't provide anywhere near the advertised wattage. And when they do, it's usually in direct bright sunlight (i.e. depending on where you are and what season it is, it can be that efficient only for a few hours, and sometimes none at all).
If you want a decent portable solar panel, get the non-flexible monocrystalline one.
If you want a decent portable solar panel, get the non-flexible monocrystalline one.