The NKG Iridium DPR8EIX-9 spark plug requires a socket size of 5/8 inch (16 mm) for installation and removal. It's important to use the correct size to avoid damaging the plug or the engine. Always ensure that the socket is designed for spark plugs to achieve the best fit and leverage.
18MM
Spark plugs use SAE and not Metric. The one that fits it is the one that fits it.
35mm
36mm.
54mm
5/8"
32mm
11/16" (18mm) deep well socket
Take a socket set and test each socket until you find the correct size that fits snugly.
7mm Hex.
36mm
32mm