James is correct. Most Denso Iridiums are damaged by incorrect fitment. They are an excellent plug and will last tens of thousands of miles in correct use. They are also pre-gapped at 0.7mm which is absolutely ideal for wasted spark conversions as luck would have it.

The ONLY negative the Iridiums have is the ultra fine 0.4mm electrode is easily shorted by excess rich mixtures so they arent the best choice for a car that does a lot of cold starts only. IE: One in storage etc...