 The reason behind the tonal difference between P-90s and Fender single-coil pickups is due to construction methods.P-90s use bar magnets set under the polepieces, much like a humbucker, whereas Fender single-coils use rod magnets as the polepieces.Popular guitars that use or have the option of using P-90s are the Gibson SG, Gibson Les Paul, Ernie Ball Axis series and the Epiphone Casino.