I have a 2007 TRX and if I'm not mistaken, it comes stock with Rancho shocks. No idea which kind, but it rides like a truck and I LOVE it!

 

I believe the 5100's are adjustable as where the hd's aren't but check with some of the other guys here as they probably know more about suspension then I do! Like I said the hd's worked great for me and are still performing perfectly!