The Krüss gemstone refractometers are offered either as a compact professional or standard version. They both provide a sharp image and good readability, and have the option to select LED illumination or ambient light with a sodium filter. They offer a measuring range of either 1.33-1.83 nD or 1.33-1.81 nD depending upon model selected, and have optical glass prisms, with accuracy to 0.01 nD and a resolution of 0.01 nD. This equipment is lightweight (at 0.4kg), and has an automatic multi-voltage power supply (110-220V). All Krüss gem refractometer models are constructed of cast aluminium, and are supplied complete with a polarisation filter and manual.