i have a lrp x-11 13.5 part #50631 and a lrp x-11 3.5 part #50711, and i understand that the 3.5 has a sintered rotor and the 13.5 does not. So i decided to take the sintered rotor from the 3.5 and put it into the 13.5. But when i had them both apart i noticed that the rotors look identical. how can one be distinguished from the other? Is it possible that the 13.5 came with a sintered rotor?