The Biotek Marine Salinity Refractometer with LED Light is a precision instrument designed for saltwater aquarium enthusiasts to accurately measure the salinity of their marine water. This refractometer features automatic temperature compensation and provides true seawater salinity readings, accounting for elements like calcium and magnesium in addition to sodium chloride. It includes an easy-to-read scale that measures salinity from 0 to 100 ppt with a precision of one part per thousand and specific gravity from 1.000 to 1.070 with the same accuracy. The built-in LED light ensures clear visibility without needing additional lighting, making it convenient for use in any setting. Its protective case, pipette, lint-free cloth, and calibration tool make this refractometer a complete package for maintaining optimal water conditions.