A multi-part injection mold (10) for producing a cuvette (1) or a receptacle vessel for liquid or gaseous media for spectroscopic, qualitative and/or quantitative analysis or measurement using a measuring region or measuring gap (2) through which radiation is able to penetrate is provided, with the cuvette being made of plastic through injection molding. To this end, the inner cavity or filling space (9) and the measuring gap (2) are formed and limited on the interior of the injection mold (10) by a contour core (11), the thickness of which is limited to about one millimeter or less in the region (11a) of the measuring gap (2). The contour core (11) is held on the end (11b) thereof having the smallest dimension during the injection molding process, initially by at least one support (14), and retracted during the injection molding process after partial filling of the mold with plastic such that the lower continuation of the walls of the measuring gap (2) is formed.