For measuring the salinity and specific gravity of seawater, and utilizes a new material that is durable against salty samples. The salinity of seawater is displayed in parts per mill (‰). This refractometer requires no battery due to optical device. Features: • Easy to read display • Screen shading. With the same measurement range as MASTER-S/Mill M, MASTER-S/Millα is an Automatic Temperature Compensation (ATC) model with water resistant properties(IP65).