This review is from: Folding Magnifier 21Mm Loupe 20X Chrome
I purchased this for botanical study. As far as I can tell it works well but I can't comment on the actual strength of magnification, it possibly feels stronger than ones that I have used in the past (on courses etc) but not having paid attention to the labels on those it is hard to say!
I have found it a bit harder to use than I expected (again compared to ones I have used before) as the lens is smaller. The area of focus is small (in the centre of the lens) with the other areas blurry. Maybe with a smaller magnification the focus is wider? That said it does magnify well and really means you can see the small details, parts of flowers etc.
For the money it is better than expected, it feels a bit cheap but does work for what I need although I may look for another with a larger lens.