Limit Thermostat Switch - 170F - Normally Closed, Open On Rise - 170F and below the electrical circuit will remain closed, 170F and up will open the electrical circuit. Automatic Reset - 3/4" Diameter.  For use on furnaces, air handlers, dryers, fans, dishwashers, package units, heaters,  limits, ect. - U.L.Rated - #L170. These limit thermostat switches are brand new and made by Napcous Corp.