This loupe can be used to estimate the weight of a mounted gemstone or to measure the table, or facets, etc of the stone. The distance between measuring scale and the lens is adjustable so you can obtain a sharp image of the measuring scale imposed on the gemstone. The measuring scale ranges from 0 to 11 mm, in 0.1mm increments. Alongside the millimeter scale, there is corresponding approximate weights for round brilliant diamonds, eliminating the need to look up a separate chart for weight estimation.