The invention relates to a nipple unit comprising a nipple (4), a fastening device (2, 3) for fastening the nipple (4) onto a liquid container (1), and a venting valve (23, 310), wherein the fastening device has a first and a second fastening part (2, 3). The venting valve (23, 310) comprises a first valve part (23) which is arranged in the first fastening part (2), and a second valve part (310) which is arranged in the first fastening part or in the second fastening part (3). The venting valve (23, 310) opens and closes relative to the second fastening part (3). The valve is preferably a membrane valve, and the first valve part is preferably a valve membrane. Said nipple unit functions very reliably even at very low pressure differences between the bottle and the environment. Furthermore, the functional range of the different nipple units of the same type is relatively narrow so that different nipple units function very similarly and the venting valves are actuated at similar pressure differences.
