A container comprising: a finish defining an opening at a first end of the container that provides access to an internal volume defined by the container ; and a base portion including a diaphragm that is concave relative to an exterior of the container , the diaphragm extending from a standing surface of the container to a center push-up portion of the base portion , the standing surface is at a second end of the container opposite to the first end; wherein the diaphragm is movable from an as-blown first configuration to a second configuration in which the diaphragm is closer to the first end as compared to the first configuration in order to reduce residual vacuum within the container , the diaphragm being generally hemispherical in cross-section and in an activated position when in the second configuration, characterized in that the diaphragm includes a transitional radius between the standing surface and the center push-up portion , at a node of the diaphragm , the transitional radius is spaced apart from opposite ends of the diaphragm a distance greater than 20% of a total length of the diaphragm in the first configuration, the transitional radius moves along the diaphragm as the diaphragm moves from the first configuration to the second configuration, the diaphragm includes an outer portion on an outer side of the transitional radius and an inner portion on an inner side of the transitional radius , the outer portion is curved and in a substantially similar position in both the first configuration and the second configuration, and the inner portion moves towards the first end of the container as the diaphragm moves from the first configuration to the second configuration. a finish defining an opening at a first end of the container that provides access to an internal volume defined by the container ; and a base portion including a diaphragm that is concave relative to an exterior of the container , the diaphragm extending from a standing surface of the container to a center push-up portion of the base portion , the standing surface is at a second end of the container opposite to the first end; wherein the diaphragm is movable from an as-blown first configuration to a second configuration in which the diaphragm is closer to the first end as compared to the first configuration in order to reduce residual vacuum within the container , the diaphragm being generally hemispherical in cross-section and in an activated position when in the second configuration, characterized in that the diaphragm includes a transitional radius between the standing surface and the center push-up portion , at a node of the diaphragm , the transitional radius is spaced apart from opposite ends of the diaphragm a distance greater than 20% of a total length of the diaphragm in the first configuration, the transitional radius moves along the diaphragm as the diaphragm moves from the first configuration to the second configuration, the diaphragm includes an outer portion on an outer side of the transitional radius and an inner portion on an inner side of the transitional radius , the outer portion is curved and in a substantially similar position in both the first configuration and the second configuration, and the inner portion moves towards the first end of the container as the diaphragm moves from the first configuration to the second configuration. <EOS>