North Mountain Supply Premium Glass Proof & Tralle Hydrometer Alcoholmeter. Made in France, Lead & Mercury Free! This proof and tralle hydrometer measures the alcohol content of distilled alcohol or spirits with a specific gravity less than 1. 000. The tralle scale has a range of 0-100 and measures the actual alcohol percentage. The proof scale has a range of 0-200 and measures the proof of the spirits or distilled alcohol. The hydrometer is calibrated to give an accurate reading when the liquid is at 60F (15. 6C). to use the hydrometer, fill a Test jar with the sample. You can use the tube that the hydrometer comes with or purchase a Test jar separately. Place the hydrometer in the liquid making sure that it is completely suspended and not touching the sides of the Test jar. Take the reading on the scale at the surface of the liquid. This hydrometer is only designed to provide a general indication of alcohol content. A more precise measurement requires the use of specialized equipment. This hydrometer is also designed to only Test Pure distilled spirits such as whiskey and vodka. It is not designed to be used with liquors that have high concentrations of sugar or other ingredients such as rum, kahlua, jagermeister, cordials and liqueurs.