Cylindrical magnifying glass: simple structure and convenient use. Widely used in printing quality control, printing dot and angle observation, printing color separation, screen printing mesh measurement, color printing and overprint error measurement, including fine identification, assembly operation, observation of pipes and metal profiles. It is an essential tool for the printing industry and the identification of circuit boards, precision electronic containers, clocks and watches, antiques, jewelry and jade articles. The most commonly used magnifying glass is 10 times, and several magnifying glasses of 20 or 30 times are the key tools and necessities for gem experts. It is easy to carry and can be used to identify the variety and authenticity of gems. With a magnifying glass, we can observe: (1) the surface damage, scratches and defects of the gem; (2) cutting quality; (3) polishing quality; (4) the internal defects of the gem; (5) Color distribution and growth line of inclusions; Wait a minute. When identifying, the gem should be placed under strong light about 2.5 cm away from the magnifying glass.