A hot-fill PET container or bottle (10) filling with a liquid at an elevated temperature has a side wall (9) extending to a lower portion including a pressure panel (11) and a base (21) in its unfolded or pre-fill position. The panel (11) is transversely oriented and has a decoupling or hinge structure or element (13), an initiator portion (1) and control portion (5) of a steeply angled inverting conical section between 30 and 45 degrees. The control portion enables the inversion of the panel (11) into the container (10) to compensate for vacuum or reduced pressure induced within the container as the liquid cools down. The base (2) can also have a plurality of reinforcing ribs (3).