The GEM Instruments Duplex II Handheld Gem Refractometer Tester is a precision tool used in the field of gemology to measure the refractive indices of gemstones. This handheld refractometer, specifically designed by GEM Instruments, allows for quick and accurate testing of gemstones on the go. It is an essential tool for jewelers, gemstone enthusiasts, and professionals in the industry to determine the authenticity and quality of various gemstones. Its compact size and ease of use make it a convenient and reliable instrument for those in the business of buying, selling, or analyzing gemstones.