Ordering eyeglasses question

When specifying glasses for my wife online I notice that when I check the “Progressive bifocal” box a number of eyeglass styles are not available. I can’t see any distinguishing features about them. So what is the reason some do not work?

I have been told that certain frames are too small to allow for the progressive lenses I need - so it is probably related to the size.

I have progressive lenses, and to make it more complicated, a prism in one lens. I’ve had smaller frames and never been quite happy with them. Larger frames have always worked better for me.