Honeywell Thermostat, 20 to 30 VAC, 0.02 to 1 A Heat, 0.4 to 30 W Power, 50/60 Hz Frequency, Changeover: Manual, 1 Heat Stages, Relay Switch, Thermistor Sensing Element, Standard Display, 40 to 90 deg F Settings, 5 to 90% RH Non-Condensing Humidity, Cycles per Hour: Adjustable 1, 3, 5, 9, +/-2 deg F Accuracy, Heat Current: 0.02 to 1 A Running, Battery Assisted Power Stealing Power Source, Round Mounting, Dimensions: 3-11/16 in Dia x 1-3/4 in D, Premier White