what is the diference in the 12a's front rotor and the rear rotor? is theres a diference. thanks

 

I want to say that the bathtub shape is different on the top then on the bottom. If you were to put the front rotor in the rear housing, then you would have to turn it to face the opposite direction to get the gears onto the stationary gear. This will now cause the front rotor to be rotating opposite the direction it would if it were in the front since you turned it 180 degrees. The shape of the bathtub would be approaching the compression side of the housing backwards from what the engineers intended.

Confused yet?