Abstract: A vacuum pump comprises an inlet flange for connecting to a vacuum chamber, where the inlet flange comprises a plurality of apertures for receiving a plurality of protruding fixing elements extending from the vacuum chamber. The protruding fixing elements comprise an enlarged retaining portion at an end remote from the vacuum chamber and a fastener receiving portion having at least one radial dimension that is smaller than a corresponding dimension of the enlarged retaining portion. A fastening mechanism is provided that comprises a plurality of slots each extending from a same side of a plurality of apertures. The fastening mechanism is configured to be rotatable between a mounting position in which the apertures are aligned with the protruding fixing elements and a sealing position in which the slots are aligned with the protruding fixing elements.