This specification applies to miniature overcurrent air-break circuit-breakers having the following characteristics: (i) They are intended for the prevention of continued overloading of electrical circuit wiring; and (ii) Have current ratings up to and including 100 amperes; and (iii) Have current breaking capacities up to but not including 10,000 amperes; and (iv) Are intended for use at low or medium voltages. Circuit-breakers intended only for the protection of electrical equipment as distinct from circuit wiring, and which are appropriately marked as such, are not within the scope of this specification.