All beers have an "as brewed" CO2 content, which plays a role in their taste and appearance. The brewer selects this level, and the correct gas mix, such as Beer Mix 55, helps maintain the balance of the beer. The CO2 component assists in maintaining the as brewed volumes, while the Nitrogen component provides the necessary pressure for dispensing.
Beer Mix 55 is a Carbon Dioxide and Nitrogen mixture used for dispensing most beer types, including some stout beers. Beer Mix 55 aims to eliminate wastage issues associated with slow-moving bulk beers.