Automatic Temperature Compensation Sea Water Salt Salinity Refractometer for Aquarium, 0% - 10% & 1.0 to 1.070 S.g. Dual Scale Hydrometer By Adeadvancedoptics Quick Results (Faster Than Your Homebrew Hydrometer) Easy and simple to use. More Accurate Than Your Homebrew Hydrometer Automatic Temperature Compensating Refractometer 5 years warranty! Ranges: 0-100 ppt of Salinity and 1.000 to 1.070 Specific Gravity