ATC Salinity Refractometer Aquarium Seawater Dual Scale 1 to 1.07 S.G.ATC Salinity Refractometer Aquarium Seawater Dual Scale 1 to 1. 07 S. G. Product details: Designed for testing the concentration of salt water and brine, ideal for aquariums, marine monitoring and quality control in research and clinical laboratories. Measures on 2 scales, specific Gravity (D 20 20) and parts per thousand (), provides a direct reading of the specific gravity and concentration of salt in water. Features automatic temperature