Siemens GFCI plug in circuit breakers are intended for use in Siemens EQ, Siemens Ultimate, ITE, and Gould load centers or meter combinations. The single pole Siemens breakers may be used in 1 or 3-phase load centers and are 120V rated. To ensure the warranty on a Siemens panel is not voided, the use of Siemens breakers is required. The GFCI is intended for areas required by code to have ground fault protection, such as bathrooms, kitchens, and outdoor circuits. Check with your local electrical inspector to confirm. The use of a double pole AFCI allows for shared neutral applications in which two circuits will share a common neutral. 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.
