Abstract: The coupling, preferably designed as a quick-acting coupling, has two sealing members (2, 3) in which the sealing surfaces are of a material having the same coefficient of thermal expansion, in particular a hard metal and having an exact clearance fit exactly inside each other without taper or pressure. There is thus no need for sealing rings, with the result that the coupling is maintenance and trouble-free and can be used for aggressive fluids as well as over a wide temperature range.