Not to step on toes but I believe its the cast hoop as well as the shell. The RN2 has some softer Asian maple integrated where the RN1 is all North American Hard Rock maple. They don't make them anymore. They are basically USA Customs but made overseas and not nearly the amount of finish options from my understanding.Thanks for the advice. Is the main difference between the RN1 and RN2 kit the cast hoop? What makes the RN1's superior? Do they not make those any more?