Aren't these directional? How are the slots on DarkneSS and RockingtheblueSS's car different? See on Darkness' car the top of the slot is facing in the direction of rotation and in Rockin's car the bottom of the slot is pointed in the direction of rotation.
A google search of "slotted rotor direction" agrees with the way Darkness has them. What's the deal on this before I go install mine.
Edit: I think I found a site
that might explain it. It says that if the internal cooling vanes are radial or straight, then it doesn't matter which way the slots go. Maybe that's the case here??