A new stopper that fits a 2.8,3,5,6, or 6.5 gallon glass carboy(DOES NOT FIT BETTER BOTTLE OR PLASTIC CARBOYS). Also fits our 500ml Erlenmyer flask. Made with a longer taper from a different material, this stopper does not pop out when wet. Much more reliable, it quickly became our stopper of choice for all applications involving these size carboys.,,Also will fit a 12 or 22 oz beer bottle when used upside down.