Non-free products include any hardware for which the driver uses closed source "blobs" like broadcom wifi, some intel wifi, video cards - also video card drivers are a problem. "Most products" might be too extreme a word. But products that you need non-GNU software to use are pretty commonplace. Or the GNU software may not be equal in functionality to the proprietary ones.
Of course any OS that uses a kernel that is not free (meaning non-Linux,non-BSD, non Hurd) would be off limits.
Don't get me wrong, the GNU guys and girls are doing noble work - and many of their programs are BETTER than the proprietary ones or very innovative. I'm just trying to make the point that the word freedom is used to demand restrictions on behavior, which I find ironic.