Abstract: A nipple comprising a teat, a mounting flange coupled to the teat defining a valve cavity therein, and a valve positioned with in the valve cavity, in which the valve is configured to equalize differing pressures. A system and method comprising a container and a nipple configured to be selectively and sealingly coupled to the container, in which the nipple further comprises a valve and valve cavity configured to equalize the pressure differences between the ambient environment and interior of the container, in which the valve cavity has a minimum volumetric capacity of 0.9 cubic centimeters, and in which the valve cavity has a stepped triangular cross-section positioned at the bottom of the valve having a minimum wall thickness of 0.8 millimeters and a minimum height of 3.0 millimeters.