I got from eBay a set of 4. My car is a 2.0 liters Mitsubishi Lancer ES with about 160 000 miles. I used other copper NGK spark plugs before on this car, I used for a long time Bosh Platinum but never had a cracked porcelain. I noticed that lately the car was missing the full power for throttle over 60% and shaking.
When I pulled out the spark plugs I found that spark plug's porcelain on cylinder 3 was cracked from top to bottom and at cylinder 4 half way. Searching google for cracked spark plug porcelain forum, I found someone else having same problem, his pictures looked like mine.
I am seriously thinking that I got a counterfeit. I still cannot believe that an original Japanese product can fail this way. So people, if you buy this product on eBay, use google to find information how to distinguish fake NGK product from the originals.
I would like to recommend these top of the notch Laser Iridium Spark plugs for your vehicle whether it's American car or Any import. This is the real deal. I know they are a little expensive but it's worth the purchase because of outstanding performance plus a great feel of better acceleration on your gas pedal. Buy these and you will never regret.