2 Micron Stone, 1/2" Diameter 1" Long. 1/4" barb. A simple upgrade for any homebrew is oxygenation. This is vital to ensuring your yeast thrive during fermentation, it also reduces the lag phase. Properly oxygenated wort will help ensure your beer reaches the targeted final gravity.
Tip: This diffusion stone can also be used to force carbonate your keg beer.