These "Made in China" plugs are out of order. The first and most frustrating thing is that the standard plug wrench will NOT fit these plugs. I tried two different keys with the same problem. The dent at the tip of the connector is approximately 2mm. The second problem is that the seals are not flat rings but are round in cross-section like a standard O-ring. I'm not sure how they will seal. This is the only time I've seen these o-rings. I would not buy these plugs again. A complete waste of money.