Siemens D130 30-Amp QO Replacement Single Pole Circuit BreakerSiemens QO replacement breakers are UL listed for use in Square D QO brand load centers and are ideal for replacement of existing breakers or if expansion circuits are required. These 3 4 Inch breaker snap on to the QO type bussing. 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