Circuit breakers protect the wires in your home from overheating (referred to as an overload) and fault currents (referred to as short circuits). The Eaton cutler-hammer 30/30 amp 1 inch duplex type BD circuit breaker is also known as tandem or circuit limiting breaker. This style of breaker will only fit into load center bus stabs that are notched to accommodate the rejection clip built into the bus bar contact on the breaker. This is a code requirement that limits the number of breakers that can be installed into a load center.