Extra large 3-Piece airlock with 50% larger capacity. Simply remove the cap, fill the cylinder about halfway (to the imprinted line) with water or sanitizer, and replace the cap. 3-piece airlocks are easy to clean with an airlock brush if the fermentation back up into the airlock. These extra large airlocks can hold even more sanitizer or water than the standard size. Great when cold crashing your fermenter or for extended aging where the airlock may dry out.