A sealing member for unsealably sealing a toner opening of a toner or developer container mountable to an image forming apparatus. In one embodiment, a sealing member has a base member, a first coupling engagement portion and a second coupling engagement portion protruding away from the base member axially, a central member protruding away from the base member axially, wherein the central member has a cylindrical portion defining an opening therein, and at least one supporting member projected radially outwardly from the peripheral surface of the cylindrical portion, wherein the central member is formed to be concentric with the base member axially and positioned between the first coupling engagement portion and the second coupling engagement portion.