there is disclosed a circuit breaker panel which is very compact , said panel comprising a panel board having a base , a bus bar support assembly mounted on said base , said support assembly having therein a plurality of separate bus bar receiving recesses arranged in alignment with each and perpendicular to said base , a bus bar in each of said recesses in alignment with each other and perpendicular to said base , and laterally spaced sets of terminals associated with said bus bars for electrical connection with a plurality of plug - in circuit breakers , respectively , said bus bars being disposed in the space between said terminals .