This is a new Furnace Microtemp Thermal Fuse Cutoff  G4AM0400 

 Thermal cutoff with this fuse offer an accurate, reliable solution to upper limit temperature protection. 

Acts as “one shot” or TCO, the Thermal Cutoff provides low cost protection against

 over-heating by interrupting an electrical circuit when operating temperatures exceed

 the rated temperature of the cutoff- 128 C or 262 F. 

Maximum operating current 250 VAC @ 10 Amps / 120 VAC @ 15 Amps