I did a search but came out empty. i was wondering what is the difference between regular UR pulleys and the SS pulleys? thank u

 

Did you visit the UR site to find the answer?

 

Well there is the Ultra S crank pulley and the Ultra SS 3 pc pulley set. Those both use an underdrive crank pulley. There is also the Ultra Sc crank pulley and the Ultra SSc 3 pc pulley set which utilize a stock size crank pulley.