The invention relates to a screw cap for containers with a threaded neck, in particular PET bottles designed to hold beverages containing CO2. Said cap comprises a top plate (1), an approximately cylindrical cap jacket (2), provided with an interior thread (3), an approximately cylindrical inner sealing collar (4), emanating from the top plate (1) and having an annular continuous region that projects radially outwards and an essentially cylindrical outer sealing collar (5), which concentrically surrounds the inner sealing collar (4). The maximum outer radius of the inner sealing collar and the minimum inner radius of the outer sealing collar differ only slightly, preferably by less than 2 mm and in particular by less than 1 mm and the inner and outer sealing collars (4, 5) are designed to receive the upper region of a bottle neck (11) in the annular gap formed between said collars. The aim of the invention is to provide a screw cap, which in general retains the excellent sealing properties of the known screw cap, even in extreme environmental conditions and is at the same time capable of limiting the pressures that occur in a container with a screw cap, without losing its sealing function. To achieve this, the cap is provided with devices (6, 7), which limit the axial depth of penetration of the edge of a bottle neck (11) into the gap between the inner (4) and the outer sealing collar (5).