Base of a plastic container

A plastic container having a base portion adapted for vacuum absorption, the container comprising a base and a container body extending up from the base along a central axis to a finish portion defining a mouth, the base including

• an outside wall;
• a chime connecting the outside wall to an annular contact ring;
• an inside wall extending upward from the annular contact ring to a circular hinge;
• and
• a diaphragm connected to the circular hinge, the diaphragm movable between a first position and a second position in response to pressure change within the plastic container, the diaphragm including a central region and a flexible wall around the central region, wherein the flexible wall includes a first portion having a curved cross-sectional profile between the central region and the hinge, a second portion having a linear cross-sectional profile between the central region and the hinge, and transition portions extending radially between the central region and the hinge and positioned circumferentially between the first portion and the second portion.