Abstract: An agricultural grain storage or feed tank including a body with a roof having an upper inlet opening is provided with a roof cap assembly which includes an elongated and vertically extending control rod which is vertically and pivotably movable with respect to the body of the tank whereby a cap connected to the control rod may be selectively moved remotely from the opening by raising the control rod and thereafter swinging the cap relative to the opening. The opening is reinforced by a reinforcing centering ring which is selectively mounted to the exterior of the roof of the tank and which includes a plurality of support rods on which the cap is normally seated so as to create an air passageway into the inlet opening. In the preferred embodiment, the body of the tank is corrugated and is supported by legs having corrugated sections which interfit with the body of the tank.