First, I don't know if these glasses are knock-offs but along the bottom edge where the lenses contact the frame there are several nicks/chips in the lenses (both) that reflect back into my eyes and generally appear like a blob of lint when the glasses are being worn (plus when cleaning them your cloth will hang up on the nicks). As far as their usefulness as described (see to read, see your computer, see across the desk) there is not much rhyme or reason as to where the sweet spots are placed. I have a normal size face but the lenses are not symmetrical. The sweet spot for the right lens is within the inside one quarter of the lens (you almost have to look at your nose to use this area) while the left lens doesn't seem to have a spot where my eye can focus; certainly there are not areas in both lenses where my eyes can both use the magnification at the same time. Lastly, the most powerful area of both lenses is right along the bottom border within about a 1/4 inch area meaning that I have to tip my head uncomfortably back in order to focus, plus there is the issue of not having an alignment between my eyes while doing this so I pretty much have to move my head left and right until I decide that it's close enough. I bought these to try and end the headaches from using a computer screen at work for several hours while I interview clients but they are way over-rated. I'd return them if my son didn't toss out the packaging, and I think I'll see if they will take them back regardless! I also want to note that I wore progressive lenses for several years before I had the lenses in my eyes replaced and never had a problem finding the focal point for the distance I had to deal with at the time.