Abstract: A Reagent container cap (116) is adapted to being mounted to a reagent container and to being adjustable, at least after an initial opening of the cap (116), between an opened state and a closed state, wherein the reagent container cap (116) defines a cap interior space (109) and has a cap opening (116o) allowing access to the cap interior space (109) from above when the cap (116) is in the opened state; and wherein, in the closed state of the cap (116), the cap interior space (109) is open only towards a bottom side (116b), wherein the reagent container cap (116) comprises a main portion (116m) and an insert portion (116i) that are fixedly connected to each other and made from different materials, wherein, when the cap (116) is in the closed state, the cap interior space (109) comprises a region (109t) which is delimited circumferentially and towards the upper side of this region completely and exclusively by surfaces of the insert portion (116i).