ive been looking around on this ite for atleast an hour trying to find something on under drive pulleys.ive been look at unothodox crank pulleys and have made my mind to get one. but my problem is that they have so many different kinds of crank pulleys on their site. not to sure what the difference it between the ultra series ultra s and the ultra sc. but then they also have the tuner series tuner s. if u could help me out with which one would be the best bang for the bucki would appriciate it