% Alcohol / Proof hydrometer. This hydrometer is calibrated to show the percent of alcohol by volume @ 20°C/ 68°F. These hydrometers are manufactured in strict accordance to specifications of the ASTM (American Society for Testing and Materials) for accuracy and design. Specifications % Alcohol Range 0 to 100% Proof Range 0 to 200 Subdivision 1% / 2% Tolerance +/- 1% / 2% Length 310 mm / 12.20"