I just replaced my RD on my Trek from a mountain bike setup the previous owner had the bike shop setup to assist him with climbing and the cassette. I also changed out my RC when I did to my traditional preferred 11-32 with a SRAM Force RD wifli medium cage. I think I paid $108 for the RD which I was hoping to source a bit cheaper but I am a SRAM junkie and love the Force tier. I would say a Rival would be easy to source and Fleabay would be one of my looking points for sure.