These orange carboy caps fit onto 3, 5 and 6 gallon standard glass carboys, and have a myriad of uses. They are most often used to prime a 3/8 in. OD racking cane. Simply place the racking cane through the center of the cap and blow into the side tube, and watch your liquid go! These caps can also accommodate airlocks, or become blowoff assemblies with a length of 1/2 in. ID tubing. Everything you need in one handy carboy cap!