The CE551R allows you to join several wires at the same time. This is especially helpful in situations when resilience against vibration is key. They provide a way to make a simple connection for electrical wiring applications. Connectors of this type are also referred to as crimp connectors, because crimping the insert helps to hold the wire connection in place. The nylon covering acts as insulation for the copper insert. The tin plating on the insert helps provide protection from deterioration.