A closure includes a skirt and internal lugs on the skirt. The skirt has an undulating circumferential contour that includes alternate outwardly convex and outwardly concave portions, with the internal lugs being disposed within the outwardly concave portions of the skirt. The skirt preferably is sufficiently flexible to allow the outwardly concave portions of the skirt to assume an outwardly convex geometry as a result of outward pressure on the internal lugs during demolding of the closure. The closure thus may be simply axially stripped from the mold core during the demolding operation without requiring movement of portions of the mold core to clear a path for travel of the lugs. The lugs preferably are shaped as an inverted U that opens toward a free edge of the skirt, further to facilitate demolding of the closure.