Ultra-thin wall thickness and magnetic properties, which is very important with a long and narrow spark plug bore. Otherwise, you will need to use a magnetic device to remove or install the spark plug. I can't find needle nose pliers that will do the job. If you don't have magnetic material to hold the new spark plug and you accidentally drop the spark plug into the hole, the tip can hit the spark plug tip and change the gap width. There may be a problem with the ignition timing of your spark plug. In any case, you may need a wrench extension to work with this nut if you have a long spark plug bore. Therefore I can warmly recommend this outlet 👍🏻