2009 rzr 800 s clutch kit

Looking for a clutch kit for my 09 rzr s.

Been noticing the epi and SLP clutch kits are for year 09 and s models only. The 09 s must have a different clutch setup then other years? Just want to make sure I order the correct kit the first time. I ride mostly trails in the woods and looking for more bottom end without reducing top speed.