This portable salinity tester features a full measuring range of 0 to 100% salt concentration, suitable for seawater, brine, pickling liquid, seafood processing and aquaculture detection. Adopting high-precision optical glass prism with built-in ATC automatic temperature compensation, it effectively eliminates data deviation caused by temperature changes and provides stable, instant readings without batteries. The ergonomic lightweight body comes with anti-slip texture for comfortable single-hand operation, and the sample trough is smooth for quick cleaning after each test. Equipped with a matched hard protective storage box, it shields the refractometer from scratches, collision and dust during outdoor carrying and long-term storage. Just drop a small amount of liquid on the prism to get clear scale data. It helps users accurately control salt proportion for food pickling, monitor seawater density for fish tanks, and standardize brine production. Compact, sturdy and easy to carry, this complete testing kit is a must-have tool for aquarists, food processors and seafood merchants.