An adapter for contacting a circuit breaker to a busbar system, with a casing having a first mounting side to attach and electrically contact the adapter to at least one busbar of a busbar system and a second mounting side to attach and electrically contact a circuit breaker to the casing, characterized in that, on the second mounting side, at least one rotary disk with several sets of threaded inserts for attaching a circuit breaker is fitted so that it can pivot around a rotational axis perpendicular to the mounting sides, wherein each set of threaded inserts is equipped for mounting a particular type of circuit breaker so that for each position of the rotary disk one of the sets of threaded inserts is positioned in a mounting position for a particular type of circuit breaker.