The disclosure is of a novel closure for air evacuated tubular containers and comprises a tubular body having flexible, elastic sidewalls, an open end, a closed end formed by a cannula-pierceable, flexible, elastic end wall having a concave-convex configuration in cross-section and a flange disposed...http://www.google.de/patents/US4295572?utm_source=gb-gplus-sharePatent US4295572 - Cannula pierceable self-sealing closure
