Drilled Rubber Stopper (Carboy Bung Sets of 3)
This is a drilled tapered rubber bung for a better seal and holds the airlock securely in place. A curved lip stops the bung from accidentally falling into the carboy. All three rubber stoppers are the same size and easily fits all 3, 5, 6 and 6.5 gallon glass carboys.  These stoppers do not fit plastic carboys or plastic water bottles.