Closing cap for a plug-and-socket connector

A closing cap for media-tight sealing of a plug face of a round plug-and-socket connector, wherein the closing cap is adapted to be detachably fixed to a plug-and-socket connector housing, wherein

• the closing cap is configured, such that a further closing cap of identical construction can be detachably fixed to the closing cap
• the closing cap has the form of two cylinders placed one over the other, which substantially form a locking cylinder and a docking cylinder with a baseplate,
• the locking cylinder is adapted to be fixed to a plug-and-socket connector housing and to a docking cylinder of a closing cap of identical construction,
• the main axes of symmetry of the locking cylinder and the docking cylinder are aligned with one another,
• and an outer diameter of the locking cylinder is greater than an outer diameter of the docking cylinder, and
• the locking cylinder is adapted be fixed in accordance with a bayonet principle to a plug connector housing and/or to a closing cap of identical construction.