6.5 Gallon Glass Carboy. Glass carboys are air tight, easy to clean and sanitize and do not hold odors. With proper care, this 6 1/2 gallon glass carboy will last for a lifetime of brewing as it will not break down over time. Unlike plastic, they are not easily scratched which lowers the risk of harboring bacteria that may interfere with the fermentation process. The clear glass also allows you to keep an eye on the fermentation. Glass detail may vary. Use with a #7 Rubber Stopper or Small Universal Bung.