The 4PU51 Dayton Heating Control Thermostat is a 24VAC Millivolt thermostat designed for HVAC and refrigeration systems. Made by the brand Dayton in the United States, this thermostat is compatible with Dayton products and is a reliable part for controlling heating systems. With its model number 4PU51, this thermostat is a crucial component for maintaining optimal temperature settings in commercial and industrial settings.