The Siemens Type BF Circuit Breaker is a panelboard mounted, non-interchangeable trip 5mA ground-fault, molded case circuit breaker available in 15-60A, 1- and 2-pole.  Available in 10KAIC and 22KAIC interrupting ratings.  Siemens strongly recommends against the use of "used" breakers.  The installation of used breakers in a Siemens panel will void the warranty on the panel.  Siemens does not sell used breakers and has not approved any 3rd party sellers to do so.