The 2 micron diffusion stone can be used for aerating or oxygenating wort, or in quickly carbonating beer in the keg. It has 2 micron holes, larger than the 0.5 micron diffusion stone and will therefore diffuse more quickly with less of a chance of becoming clogged; however, gases will not be diffused as well into solution. It features a 1/4" barbed stem for attachment to tubing. These are often used in aeration or oxygenation systems, but can also be attached to the dip tube of a keg for quick carbonation of beer.
It is recommended to boil the stone after use in order to clean and sanitize. Avoid touching these stones with your hands, as oils from your skin can get into the pores of the stone and cause clogging.