The present invention is directed to a lid (5) with a central lid portion (6) and with a peripheral clamping groove (7) formed between an outer groove wall (8) and an inner groove wall (9) for being clamped onto a beaded rim (4) of a cup-shaped receptacle (1). A constriction (10) is provided on at least a peripheral section of the outer groove wall (8), the constriction (10) forming a projection (14) into the interior of the groove (7), this projection (14) comprising a projecting tip (15), an upper wall (16) and a lower wall (17), and the projecting tip (15) defining a horizontal plane (H). The invention is characterized in that an angle (α) between the horizontal plane (H) and a tangential plane (T16)to the end of the upper wall (16) adjacent the projecting tip (15) is smaller than an angle (θ) between the horizontal plane (H) and a tangential plane (T17) to the end of the lower wall (17) adjacent the projecting tip (15).