Abstract: A molded screw-threaded plastics closure has depending from the underside of the top an annular sealing portion spaced inward of the skirt. The sealing portion includes a plug part with a sealing rib for engaging the internal surface of the neck of a container, a radially outwardly projecting flange above the plug part, and a waisted pivot part disposed between the flange and the top. As the closure is applied, the sealing rib first moves into sealing engagement with the bore of the neck of the container, and then the flange comes into engagement with the top of the neck of the container and causes the sealing portion to pivot outwards about the part to tighten the seal. An internal rib on the skirt engages the outer surface of the neck of the container to form a secondary seal. Forms of stop may be provided for limiting the movement of the closure and/or the pivotal deflection of the sealing portion to prevent over-tightening during application of the closure.