I am using Merlin Turbo and Nelson plugs. The Nelson's have a regular hex which my igniters works with. The Turbo one is heavy duty. I would think a cool for high nitro, and if it runs good, use it all the time because cools are a bit tougher normally. I haven't really used anything else. I bought a P3 (extra hot) OS plug to try on gas, but haven't done that yet. Oh, the Merlins are $5 which is cheaper than most others. I guess I am saying to experiment, but hopefully someone else can give you first hand comparisons to save you from buying 10 different brands.