Abstract: A flexible, plastic lid for sealing containers such as drums and pails having an open top formed with a contoured lip includes a center portion and an annular edge portion extending radially outwardly from the center portion. The annular edge portion comprises an inner curl, an outer curl and an intermediate curl disposed therebetween. The outer curl is formed with a convex inner surface having spaced projections which is adapted to flex and stretch over the contoured lip of the drum so that the inner surface, including the spaced projections, engage the lip to form an effective seal therebetween. A number of locking clips are spaced at regular intervals about the lid and are adapted to snap-fit over the lid and against the lip of the container to enhance the seal therebetween.