Magnifiers, whether pocket, handheld, loupe or hands free all follow some basic rules of optics. When ordering, keep these rules in mind.
As magnification goes up in a magnifier, lens size goes down. A 2x magnifier, such as the Bausch & Lomb 2" x 4" Rectangular 2x has a lens size of 4 inches. This is suitable for reading a book or text or just taking a look at things in general. On the other hand, a 10x magnifier, such as the Nikon 10x Jewelry Loupe Jeweler Pocket Round Magnifier - 6947 has a lens size of about a 1/2 inch or less and will therefore offer a much smaller "window" to see things. It is great for high magnification and a super close look at many objects, but it will not perform as well if reading a book. Unfortunately, you can't have it both ways, so you need to decide if magnification or lens size is more important for your application.