Vin Table's silicone fermenting and ventilating bungs have created more options for the Winemaker in creating a special blend. This #7 silicone bung is the perfect size for sealing 5.0 gallon (20L) glass carboys, for use with an airlock or tubing. Vin Table silicone bung is highly stable and designed for long lasting, withstanding a temperature range of -100°F to 400°F Tested with Shore Durometer, this bung was graded with a Shore A hardness of 40, so no need to worry about cracking, chafing, mold, and mildew.