Universal bungs have a longer taper than standard rubber stoppers, for snugger fit and better seal—plus a lip that prevents the bung from falling into carboy. The drilled hole fits an airlock (#7008 or #7010) for fermentation.
This universal bung will work with plastic carboys, Better Bottles and Bubbler PET fermentors.
Top Diameter: 2.375"
Bottom Diameter: 1.656"