Limit Thermostat Switch, Automatic Reset - Normally Closed, Open On Rise, 300F and below the circuit will remain closed. Circuit will open at above 300F - 3/4" Diameter. For use on furnaces, dryers, fans, dishwashers, limits, package units, heaters, ect., U.L.Rated, #L300. These limit thermostats are brand new and made by Napco USA Corp. and distributed by Supco Corp.