This fits 1/4" i.d. tubing, and can be fitted to the end of the gas-in dip tube inside a Cornelius style keg to force carbonate beer much more rapidly than simple gas pressure. The .5 micron stone releases tiny bubbles to allow gas to dissolve very quickly. Due to the extremely small size, buildup (mineral deposits, oils, and organic matter) can clog the stone over time. Can be used to build your own wort oxygenation system, or to replace a clogged stone in an existing system.