a measuring cuvette , for the spectroscopic analysis of a gas sample in a ray path between a radiation source and a detector , preferably suitable for use in a gas - measuring device , has a vessel wall that at least partially encloses a sample space for receiving a process gas . at least one window element , through which electromagnetic radiation can be coupled into the sample space from the outside , is indirectly or directly connected with the vessel wall . an inlet as well as an outlet are included , through which the process gas can be introduced into the sample space and can be removed from the sample space . at least one fastening element makes possible both secure fastening of the window element on the vessel wall and separation of the window element from the vessel wall without destruction .