A plastic pressure container including a main body portion and a finish portion defining a mouth, the finish portion has an inner surface, an outer surface and an upper rim proximate the mouth. The inner surface has an inner undercut defined therein proximate the upper rim, and the inner undercut has a curved shape in cross-section. The outer surface has an outer undercut defined therein proximate the upper rim, and the outer undercut has a polygonal shape in cross-section. The inner undercut defines a first depth relative to an inner diameter D2 proximate the mouth and the outer undercut defines a second depth relative to an outer diameter D3 proximate the mouth. The second depth is different than the first depth.