Mason Hygrometer is an air humidity measuring tool. There are two alcohol thermometers mounted on a plastic frame with a hanger. The end of one of the thermometers wrapped in cloth and dipped into a water container.

This tool is able to measure the temperature in range -5 to 50 degrees Celsius with an accuracy of 0.5 degrees. Each thermometer has two scale units, Celsius and Fahrenheit. There is also a cylindrical conversion table.

This tool comes with a user guide.