0.5 micron stone
316 Stainless
1/2" diameter. Stone is 1" in length. Overall length is 1 7/8"
The barb is 1/4" OD

How to Use the Diffusion Stone
*The “Stone” sits inside the keg near the bottom.
*A hose barb attaches it to a length of tubing (generally about 2 feet of 1/4” ID thick wall vinyl hose) which is affixed to the short downtube under the “in” or “gas side” post.
*When the CO2 is connected, it sends a tremendous number of gas bubbles out through the beer. The miniscule bubbles create a huge amount of surface area to help absorb CO2 rapidly into the beer. This is actually a miniature version of a device used by commercial breweries everywhere.
*Carbonation should be virtually instantaneous, though the manufacturer recommends carbonating your beer at least a few hours before serving.

To Use: 
Attach 2 feet of 1/4" tubing to the stone and the "gas in" dip tube inside the keg. (Tubing not included). Set your desired pressure on the regulator and gas gets emitted through the .5 micron stainless stone. The bubbles rise through the beer creating so much surface area contact between gas and liquid that the absorption rate is very rapid. This is very similar to how beer is carbonated in breweries.