The GIA Duplex 11 Refractometer is the only meter designed to spot read cabochons or smaller faceted diamonds with diameters less than 1 millimeter.   This top-of-the-line desk model has a removable eyepiece magnifier that enlarges the RI scale image. The hinged lid protects the glass working area from dust and abrasion.  See the GIA Duplex 11 Refractometer and more great tools at Stuller.com/tools.