2 INCH W X 2 1/4 INCH D X 5 5/8 INCH H SIZE; 24 MIN. AC VOLTAGE RATING; 30 MAX. AC VOLTAGE RATING; 50/60 HZ FREQUENCY RATING; BOILER, DUCT, HEAT EXCHANGER, PIPE, TANK APPLICATION; 24 TO 30 VAC VOLTAGE RATING; SURFACE MOUNTING