Salinity Refractometer is designed for testing the concentration of salt water and brine and used for quality control in research and clinical laboratories and marine industry. Its scale provides a direct reading of the specific gravity and concentration (part per Thousand) of salt in water. One scale checks the NaCl levels with the range of 0-100 ppt (with 1 ppt scale divisions) and the other scale gauges Specific Gravity with a range of 1.000 to 1.070 (0.001 accuracy). Both enables the direct determination of salinity in water that contains dissolved salt and little or no other dissolved solids. It is suitable for a marine saltwater tank.