Thermal Cut-Off Fusible In-Line Fuse Link 257F. Opens On Rise at 257 degrees F. For use on furnaces, dryers, fans, dishwashers, limits, ect., U.L.Rated, #NTC257. Approximately 3 1/8"L. Rated at 15 amps resistive @ 277V. Thermal cut-offs provide protection against overheating when the design limit temperature of a circuit is reached. Thermal cut-offs are temperature sensitive, one-time devices which open the circuit when operating temperatures exceed the rated temperature of the cutoff. These Thermal Cut-Off fuse links are new and made by Supco/Napco US Corp.