YEME Automatic Temperature Compensation Salinity Refractometer Salt Water Aquarium 0% - 10% & 1.0 to 1.070 S.G. Measure salt water or salinity of water, ideal for aquariums and marine monitoring Measures on 2 scales, Specific Gravity (D 20/20) and parts per thousand Features automatic temperature compensation (ATC) Comes with hard case, dropper, screwdriver and cleaning cloth High quality and accurate testing result