Refractometer is an optical device (no batteries) dual scaled 0-100% specific gravity: 1.0 to 1.070. Calibrate with distilled water. Adjustable eyepiece, carrying case, pipette and calibration screw driver included. *this model is ATC (automatic temperature compensating)*

The RHS series are designed for testing the concentration of salt water and brine. Provides a direct reading of the specific gravity and concentration (Parts Per Thousand) of salt in water. It provides reliable refractive index and salinity readings of total dissolved solids of aqueous solutions.

A must for any serious marine hobbyist.