A storage tank orifice flexible center mount sealing device comprising a first annular member being substantially flexible having a annular channel, a central orifice and a mating surface, wherein the mating surface is operably configured to be disposed against a wall of a container; and, a second annular member being substantially rigid having a central orifice, wherein the second annular member is disposed in the annular channel and the members are coaxially aligned. The sealing device further comprises a sealing boot disposed on the first annular member, wherein an enclosed environment is defined by the first annular member, the wall and a conduit, which passes through the wall, the central orifices of the first and second members and the sealing boot, wherein mounting hardware used to secure the first and second members to the wall are protected in the enclosed environment and first annular member has a boot mounting area.