These are well-designed, lightweight, comfortable to hold AND the lenses are about the best you can buy.
If, for instance, you compare the strongest (60mm diameter, £39.00) with the Russian hand magnifier (50mm, £5.00) you can see immediately that they are the same magnification But after comparing them for five minutes you will notice that the Zeiss magnifier is sharp to the very edge, and that the print appears far blacker and sharper than the Russian magnifier, this DOES make all the difference if you have been struggling with cheap magnifiers.
You will also notice that it is the larger (and less powerful) magnifiers that are more expensive. That is because large lenses are more difficult to make when aiming for a perfect image.