This cheap 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. It"s FULLY EQUIPPED with ATC that automatically adjust itself to correct temperature discrepancies during use. Capable of measuring with high accuracy and provides precise results. It"s equipped with vivid and sharp reticle chart for easy and comfortable reading. It uses ambient light only and no batteries are needed. This unit is a moderate quality unit that is unlikely to break down!Specifications:Measuring Range:Salinity: 0-10%Refractive Index: 1.000-1.070 Minimum Division: Salinity: 0.1%Refractive Index: 0.001(ATC) Temperature Compensation Range:10°C-30°CDetermines the amount of dissolved salt and dissolved solids Approved by strict quality and safety standards Durable and built to last long Heavy-duty and lightweight with its aluminum construction Easy to focus and calibrate Accurate testing results guaranteed Cushioned with soft & comfortable non-slip rubber