B48 / B58 Alternator Overrun Pulley

The alternator overrun pulley for the B48/B58 allows the alternator to freewheel when the engine is trying to decelerate. This has many benefits. It saves your crank balancer from trying to tear itself apart and also makes the engine run smoother and shift more rapidly. Longer writeup coming soon. 

Fits all B48 and B58 NON HYBRID alternators.

This also does not fit the Mini Cooper or X1/X2 with transverse engines. 

If your engine has a 6 rib belt it should fit. There are many variations of the alternator but if the12318634167 fits your car then it will fit what is already on your car.