I bought these through Amazon Prime. Six NGK Laser Iridium spark plugs for $25. That low price should have been a big red flag. When I received the plugs they had numerous characteristics of counterfeit plugs. Number stamped on the girdle "C9YM"...no website address on the box. No dimple on the treaded top nut. Non centered NGK IR lettering on the insulator body...etc. Clearly fake plugs. I have alerted Amazon to the problem and I am returning the plugs. They still are selling them however.