Portable Refractometer * Precision refractometer measures salinity & specific gravity * Easiest and most accurate way to maintain ideal salt levels * Professional testing device at an affordable price Test concentration of salt in several aquariums with this portable, economical, and lightweight refractometer. Featuring the same accuracy as more expensive models, this optical device provides a direct reading of specific gravity and salinity in water. Requires no batteries and automatically compensates for temperature. Portable Refractometer? Professional testing device at an affordable price - easiest and most accurate way to measure salinity and specific gravity. Temperature Correction: Automatic from 50-86°F (10-30°C) Reading: Dual scale, 0-100 ppt salinity and 1.000-1.070 specific gravity Weight: 10 oz.