6 Gallon Glass Carboy. Glass carboys are air tight, easy to clean and sanitize, and do not hold odors. With proper care, this glass carboys will last for a lifetime of brewing as it will not break down over time. Unlike plastic, they do not easily scratch so there is a lower risk of harboring bacteria that may interfere with the fermentation process. The clear glass also allows you to keep an eye on the fermentation. Use with a #6.5 rubber stopper, #7 rubber stopper, or Small Universal Bung.