Abstract: A thermal cut-out which is adapted to open an electrical circuit in response to an excessive rise in temperature associated with the circuit protected by said cut-out. Said cut-out comprising a hollow body of electrically insulating material and having an opening through which a pair of contact members are put into said hollow body. A plug of electrically insulating material closing said opening and stressing the contacts to a condition in which they are biased apart. Said contact members being retained in engagement by an element as long as its temperature has not reached a predetermined temperature. Said element being made from a material which deforms or collapse at said predetermined temperature so that it cannot retain said biased contacts any longer in engagement and permits the contacts to open.