A closure system for open headed containers utilizing a thermoplastic closure of the type having a disk and skirt depending therefrom the skirt portion including an annular ring adjacent its lower extremity adapted to lie beneath and radially inwardly with respect to an outwardly directed annular protrusion...http://www.google.com.hk/patents/US5954220?utm_source=gb-gplus-share專利 US5954220 - Dangerous goods closure system
