The package works because it has a patented pressure pouch, inside the bottle with the beer, which inflates to a constant 15-20 pounds per square inch of pressure and keeps the beer fresh and carbonated for several months. The pressure pouch is not attached to anything and floats freely inside the bottle. As beer is dispensed, the pressure pouch expands and completely fills the bottle. The pressure pouch contains food grade chemicals that mix on demand to produce CO2 gas, which maintains pressure in the bottle. This gas remains in the pouch and doesn't contact the beer.