Aeration is beneficial because it supplies yeast cells with oxygen needed for reproduction and fermentation. System includes an electric aerator pump, sanitary air filter, and 2 micron diffusion stone. Aerate your wort after cooling and BEFORE yeast is pitched. Aerating hot wort can cause off flavors in the finished beer in the same way that aerating beer during fermentation will. Pump delivers ambient air - no oxygen tank or other supplies required. No assembly required. Carboy and bung not included.