#9.5 Food-Grade Rubber Stopper - Drilled for Fermentation AirlockThe #9. 5 Rubber Stopper is a specialized fermentation seal designed for use with large carboys and specific wide mouth vessels. This food grade white rubber stopper features a pre drilled 3 8" hole, perfectly sized for standard 3 piece or S type airlocks. It provides a 100% airtight and liquid tight seal, ensuring your fermenting beer, wine, or mead is protected from oxygen and pests while allowing CO2 to vent safely. Sealing Pro Tip: To prevent the