The BPR6ES spark plug typically requires a 5/8-inch (16mm) socket for installation and removal. This size is standard for many automotive spark plugs. Ensure you have a spark plug socket with a rubber insert or magnet to help secure the plug during installation.
18MM
Spark plugs use SAE and not Metric. The one that fits it is the one that fits it.
35mm
36mm.
5/8"
54mm
32mm
11/16" (18mm) deep well socket
Take a socket set and test each socket until you find the correct size that fits snugly.
32mm
7mm Hex.
36mm