Thanks to HBF Reader Doug for this tip!
100 Pack of Rubber Grommets – 3/8″ ID by 5/8″ OD. Grommets are used to add an airlock port to a vessel. Generally speaking, you’d drill a 1/2″ hole and pop the grommet in. I’m not sure exactly what size hole these would use, although from the dimensions given, my guess would be 1/2″.
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