what are you guys talking about when you mention 3/3 or 3/3.5??

So the smart diffs are that good eh?? I was wondering how nice they would be. So i guess i gotta add those to my amain order as well?? Just 2?? or all 3 or what?? Im the type of person that seems to always want the latest and greatest and the best. So if it requires all 3, then im down!