Bullet banana connectors are used to connect ESCs and motors or any other connection.

 Features:

    High quality.
    Hook up a brushless motor to an electronic speed control.
    Low resistance, and provides the best electric flow.
    Female Internal Diameter: About 3.5mm / 0.14"
    Female Connector Length: About 12mm / 0.47"
    Male Internal Diameter: About 4mm / 0.16"
    Male Connector Length: About 12mm / 0.47"