Thermco® Sling Psychrometer, 8 .25 L x 1 .25 W x 0.625" H
Sling Psychrometer, 8.25 L x 1 .25 W x 0.625" H, Plastic, 0 to 120°F, with Spirit Filled Thermometer, Slide- Rule Calculator, For Relative Humidity Measurement, Slide-Rule Calculator Gives Direct Readings