Air Stone 2 micron
This 2 micron air stone is used to diffuse CO2 into smaller bubbles to speed up carbonation. Smaller bubbles means increased surface area which in turn leads to faster carbonation.
This stone can be used to oxegenate your wort as well, the same principles apply to saturating the wort with oxygen to promote yeast growth.
The pores in these airstones are easily blocked even by the oils from your skin, so wear gloves when handling. A blocked airstone can sometimes be cleaned or unblocked by soaking in a light solution of phosphoric acid (Stellarsan is perfect) while pushing CO2 through.
Store your airstone in a sample jar or ziplock with sanitiser when not being used for a short while. Carefully dry out and store in a ziplock bag with silica crystals for long periods. Always sanitise before use.