The FGS folding linen tester has become the standard for most of the citrus growers in Florida to examine for rust mites. It has a scale on the bottom of the viewing area that allows the user to measure the number of insects per square inch. There is a fairly large viewing area which the growers like and the 6X is enough power for most of the insect population. If you needs are to measure the number of items, bugs, etc per square inch then this is the lens for you. These lenses got their name, linen testers, by use in the clothing industry to examine fabrics. They're also very popular in the printing business to check the number of dots per inch on printed material. The majority of our customers use this lens to monitor insect populations.

The collapsible pocket magnifiers differ from the folding magnifiers in that they provide a fixed focal distance, no adjusting for focus. Please note, however, that the size of the viewing area decreases in proportion to the magnification. Before purchasing we suggest that you visit our lens diameter comparison charts. For help in determining which is the proper hand lens for your particular application please visit our planet school site:"The Eyes Have It"