Features: 1、ATC FUNCTION: Brine refractometer with automatic temperature compensation minimizes the effect of temperature on accuracy, allowing you to obtain accurate results. 2、DUAL SCALE: The seawater refractometer has a dual scale specific gravity, allowing you to obtain results in two different units with a single test. 3、EASY TO USE: After calibration, place 2-3 drops of sample solution on the prism, facing the light, and then you can get an accurate reading through the optical eyepiece. 4、DURABLE MATERIALS: The brine refractometer is made of aluminum and ABS rubber, which is rust proof, non staining, wear resistant and durable. 5、BROAD USE: The salinity refractometer is designed to measure the salinity of water and brine and is ideal for aquariums, marine monitoring, agriculture, fish farming, and brackish pools. Package included: 1 x Salinity Refractometer 1 x Dropper 1 x Screwdriver 1 x Soft Cloth 1 x Instruction 1 x Storage Box​