The Powercore 2 is the newer updated version, so it has more to do with what type of bike or ATV you have as to what one you would get, say if you had a 1992 RM125 you could only get the Powercore as if you had a 96 you would get the Powercore2
All FMF part numbers varying depending on the bikes make, model and year, I will recommend you to phone us. Just inform the Sales Agent which bike you are putting this on. Just so you know, we sell parts only by application. Meaning if you put in your "Ride", the website will only sell you what fits your "Ride".