The 6.5 gallon glass carboy is a great fermentation vessel for 5 gallon batches of beer. The extra head space in the carboy can accommodate the rising krausen that inevitably comes with vigorous fermentations. Being completely clear, every aspect of fermentation is visible. This eliminates the guesswork that goes along with trying to figure out what is going on inside plastics fermentation buckets. In addition, glass is a more inert material than plastic, which makes it a better material in which to ferment. Plastics (even food grade plastics that are used in fermentation) are prone to scratching and absorbing smells over the course of time. Scratches can harbor dirt and bacteria which can lead to off-flavors. Glass, however, does not have these problems. Try fermenting in glass today and see what the fuss is about!