Automatic temperature compensation -dual scale -salinity range 1 to 100Ppt -specific gravity: 0.001 -accuracy 0.1% -anti-slip rugged body this rugged, lightweight aluminum body refractometer has all the features & precision of much more expensive models. The dual scale also reads specific gravity to within 0.001 includes a solid storage case, pipette, cleaning cloth & instructions. Use with aqualife refractometer calibration standard solutions for the most accurate readings.