[COMPREHENSIVE MEASUREMENT RANGE] This Gem Refractometer features a measurement range of 30 to 1.81 RI, allowing you to accurately determine the refractive index of various gemstones. With a minimum graduation value of 0.01 RI, it s precise results for both professionals and hobbyists. [LIGHTWEIGHT AND PORTABLE] Designed for convenience, this refractometer is compact and lightweight, making it easy to carry in your pocket or bag. Perfect for gem enthusiasts , it fits seamlessly into your jewelry toolkit. [ APPLICATIONS] for assessing pendants, bracelets, and other gemstones, this tool is essential for anyone in the jewelry industry or gemology field. It aids in identifying both uniaxial and biaxial crystals through birefringence measurement. [ CONSTRUCTION] Crafted from sturdy materials, this refractometer is built to withstand regular use while meeting strict safety standards. Enjoy a reliable tool that promises long-lasting performance without compromising on accuracy. [SIZING REMINDER] Please refer to your own size chart rather than Amazon's size chart to the best fit for your needs.