RWRP (Reverse-wound, Reverse-polarity – magnetic pole reversed and wire wound in the opposite direction compared to the other single-coil pickups in the same guitar which alows to receive hum canceling effect in middle position).
A stock middle coil will have more mid-range on the middle positions of the 5 way selector and not be hum-cancelling. You’ll also notice marginally more volume across the whole set of 3 coils.
