This 3 piece airlock or fermentation lock is filled partially with liquid (water/sanitizer) and it sticks in the top of a drilled stopper and onto the top of your fermentor. It allows the fermentation gasses to escape without allowing anything to contaminate your fermentor. The benefit of the 3 piece design is that it is much easier to clean than traditional S or Bubble type air locks. You should always have plenty of these on hand. This listing is for 10 individual Airlocks. This listing also includes 10 grommets which are great for bucket installation to give a good tight seal.