The invention proposes a fastening element for fixing an attachment element to the projection of a syringe or carpule, which projection has at least one protrusion on its outer surface, wherein the fastening element (1) has an annular main body (3) on which an annular element (13) is articulated such that said annular element engages around the projection in an assembled state. The annular element (13) is characterised by: an annular first wall section (15) which is articulated on the main body (3) via a first mounting region (19)； and an annular second wall section (17) which is articulated on the first wall section (15) via a second mounting region (21), wherein the two wall regions (15) and (17) are preferably resiliently connected to one another and enclose a free space (23) between them, and wherein the first wall region (15) is connected resiliently to the main body (3).
