A two-piece stopper includes a stopper core and a stopper sleeve. The stopper core includes a core body, a top flange and a sleeve flange. The top flange is formed on a top of the core body and the sleeve flange is formed on a bottom thereof. At least one hole is formed through the core body to receive a glass tube or the like. At least one o-ring groove is formed in the at least one hole. An o-ring is inserted into each o-ring groove. A counterbore may be formed in the core body to receive a hose barb. The hose barb is threaded into the counterbore to retain a flexible tube. The stopper sleeve includes a cylindrical inner diameter and a tapered outer diameter. The stopper sleeve is retained between the top and the sleeve flanges. A second embodiment of the stopper utilizes the stopper sleeve only.