Universal Liquid Moisture Indicator Site Glass 1/4"
 
For optimum performance a cooling system must have a solid column of light at the expansion valve. * A sight glass provides a visual indicator of any "bubbles" in the refrigerant stream that could adversely effect performance. *
 
In general, the sight glass should be located as close to the expansion valve as possible. * Sight glasses also incorporate a visual moisture indicator which changes color if moisture is rises to an unacceptably high level.