These Spark Plugs really work! They are delivering excellent gas mileage in hot or cold weather. Starting is better as well. I have gone ahead and purchased these Plugs for my 4-cycle lawn mower engine, 4-cycle snow blower engine, 2-cycle string trimmer engine, with excellent results in all. Highly recommended! They are made out of conventional materials and yet last forever. They are much cheaper than the Iridium or Platinum types. Check out their web-site and other reviews. You don't even have to worry about gapping these plugs ........ ever.2 Thumbs up!