SB = Super Bike Class (very little mod restriction)
SS = Super Sport Class (very close to stock)
They are then separate into weight classes: Heavy [HW] (liter), Middle MW, Light [LW] (sv + others), Ultra Light [UL] (500 or under…I think) some GT classes.
I am now forced to run in LWSB, but I plan to run in LWSS.
600 is more expensive to run.
Rule Book: http://www.lrrsracing.com/2011/2011_LRRS_Rulebook.pdf