Purpose-built plugs for G23 hybrid engines using an F23 block with an H22, F20B or H23 VTEC cylinder head. They seal the two additional cylinder-head oil drain-back passages that are not present in the F23 block without welding or tapping the head.
Each plug uses three oil-resistant Buna-N O-rings and has a threaded lower section so it can be removed later with an M6 bolt.