This is a plug-in base for 4 poles Compact NSX 100/160/250 circuit breakers. The plug-in base is part of a complete plug-in kit. A plug-in configuration is made by adding a plug-in kit to a fixed Compact NSX device. A plug-in configuration allows to install or extract rapidly and easily the circuit breaker from its base. This operation can be done without connecting or disconnecting the power circuit.