A plastic container having a sidewall defining a chamber and having an opening at one end into the chamber; a base extending from the sidewall and closing the second end, the base having an outer perimeter portion defining a support structure, an axially inwardly extending perimeter wall spaced radially inwardly from the support structure forming an angle with a plane normal to an axis of the container of less than about 90°, and a flexing panel closing an end of the perimeter wall, the flexing panel moveable along an axis of the container from a first position where a central portion of the panel is below a top portion of the perimeter wall to a second position where the central portion is above the top portion of the perimeter wall to change the volume of the container; and a plurality of circumferentially spaced radial grooves on the panel.