Abstract: A container coupling suitable for connecting an aperture leading to the interior of a container with a duct for the supply or return of conditioning fluid, the coupling having a first end for connection to the duct and a second end for releasably sealingly engaging a flat sealing surface surrounding the aperture in the container, and the second end of the coupling being movable relative to the first end between a withdrawn inoperative position and an extended sealing position, the coupling having an annular body extending in sealing engagement between said first and second ends and wherein a rolling diaphragm is provided preferably between each end of the annular body and the associated end of the coupling, the rolling diaphragms being in sealing engagement between the body and the coupling ends and defining an annular inflatable space to which fluid may be supplied or exhausted for operating the coupling, there being hinge means connecting the two ends of the coupling together and there preferably being an a