Heres the new BSG grommet introduced in 2023 along with their great new buckets. Its a soft red flexible rubber material set up to push into a 1/2" hole to fit all beer and wine making buckets, caps, and lids with a standard 1/2" hole. Does not lock in the hole but fits snugly. Has a 3/8" interior hole to securely fit any "S" or "Three Piece" airlock. 1/4" Thick. Grommets seem to hide when you need them most - stock up now!