The disclosed storage drum gasket is of annular configuration, substantially symmetrical in cross-section and having inner and outer faces, with an enlarged substantially arrowhead shaped nub or protrusion running centrally around the outer face of the gasket. The gasket is elastic, allowing its inner face to be fitted over the drum rim and the nub to be generally centered on the outer side of the drum rim. Thus, positioning a drum cover over the drum top opening will fit a free edge of the cover lip against the gasket near the neck of the arrowhead. Further, tightening a locking ring onto the drum rim-cover lip will compress the gasket at the nub against both sides of the cover lip at the edge, and immediately adjacent thereto against the drum rim, in the annular multiple sealing regions generally centered relative to the drum rim and locking ring. Other interface sealing regions conventionally between the cover lip and drum rim will also still exist, improving the drum sealing capacity with the improved gasket. The gasket might be particularly effective against leakage incidental with deformation of the drum-cover structures.