Hydrometers measure the specific gravity of liquids or soil grains that are too fine for sieve analysis. The free floating device features a cylindrical stem with a ballast bulb bottom. Weighted with metal instead of lead or mercury, users simply read the graduated cylinder measurement at the meniscus. Optically clear for exact conclusions and accurate readings, hydrometers may come calibrated for specific tests. Range subdivisions and accuracy levels differ among the relative density analyzing instruments. Ethyl alcohol hydrometers can measure potential alcohol content which helps one to calculate the alcoholic content by measuring the difference of original gravity and final gravity.