Abstract: An improved, long lasting sealing ring for closing the open end of a can while vacuum is applied thereto to test for porosity. The ring comprises an outer pad of soft elastomer material made preferably of polyeurathane of relatively low durometer and having an internal cavity with a peripheral groove into which is fitted a mounting assembly comprising an annular steel or metal adapter plate encased within a relatively hard durometer elastomer, preferably polyeurathane, disk which has a novel sharp-edged peripheral configuration which functions to embed into an inturned flange on the pad and thus effectively seals the disk with the pad.