Well I am no expert thats for sure, all i know is for the beginner going through the hassle of jetting especially if you have dual carbs can be a long and scary ordeal. I myself used to always go and buy the jets and experiment but when i bought my new raptors i went with dynojet and they were right on the money for the mods i was doing. I would recommend them to someone who does not want to have to rejet over and over and wonder if their plug check is accurate. Just my experience.