The glass Carboy is a common primary and secondary fermentation vessel. Ranging from 3 gallons to 6.5 gallons this versatile container is impervious to oxygen making it an ideal secondary fermenter. If being used as a primary fermenter it is suggested to use a blow off tube for the most vigorous part of the fermentation. Cleaning of a carboy can be tedious but with the ability of not scratching is more sanitary. Use of a cover should be in place when using a carboy because light will prematurely "skunk" the beer.