Looks like either a gen 4 or maybe a 5. Does it have tribal graphix on top of the head? If so its a Gen 5 if it just says Go 5 port its a 4. Either way your okay they are pretty much the same mill. get a set of restricters they are a must with the 5 port in buggy. use the smallest 1 and you will still have more power than you need. And with the carbons and 1.0's if you find you want more of the line snap, trim alittle material off the shoes. I used to run alums but will never again in buggy just a waste of time and money if you ask me. Truggy yes they are needed. I mean to offent nobody thats just me. Bearings last way longer and I can go 4 race days easy on a set of $8 shoes and $1.29 springs.