Hot-fillable, blow molded, wide-mouth plastic containers having a pair of flex panels (11, 111, 211) for accommodating thermally induced volumetric and pressure variations while affording easy contents scoopability, and desirable labeling features. The containers are capable of being blow-molded from injection molded preforms or from extruded parisons. The containers may be hot-filled and retorted. A desirable base (27, 127, 227) for a retortable container is also disclosed.