Size:30x 21mm Loupes are used in a number of industries, notably the jewelry trade, watchmaking, photography, printing, dentistry, education, ophthalmology, geology, & biology. Amateur naturalists may also find a hand lens or a loupe a useful tool when looking at or identifying species. They are also used in numismatics and stamp collecting. The 30x 21mm loupe from Hobby Tool Supply is a perfect, basic loupe that can be used easily and effectively by anyone.