Grommet is used to create an airtight seal between your lid hole and the airlock. Arishtam’s Grommet has an 8mm ID (internal diameter) making it suitable for most airlocks ( especially S type and 3 Piece Airlock), blow-off tubes, and brewing attachments. It is made from food-grade Nitrile N70. Therefore, it does not crack or give off foul smells making it perfect for home brewing.
Take any plastic lid of your fermenter. Subsequently, use a soldering iron or hot iron nail to drill a 12mm hole for this grommet. Do a pressure test to check if the grommet seal is airtight.