Our Jewelry Refractometer ismade of plastic material which is for long term use and it can provide a longer service life and a lower replacement frequency With this Refractometer, you can identify singly & doubly gemstones quickly and accurately This Compact Refractometer will be your primary and most powerful tool in gemstone identification The Portable Refractometer is a low cost, lightweight measuring instrument but with high wccuracy The Gemmology Refractometer has been uniquely designed for a low battery consumption and easty to carry with to anywhere you like