Simple, Spacious, Secure. The Siemens Plug-On Neutral Combination Type AFCI breaker detects arcing faults (an unintentional arcing condition in a circuit) that standard circuit breakers are unable to detect. This AFCI circuit breaker is the same, reliable design, without the pigtail, specifically design for the Plug-On Neutral Load Centers. These breakers now only have a single load lug. The branch neutral conductor is returned to the neutral terminal bar for simpler and quicker wiring.