4x6 is the correct size. You have to be careful as to the depth needed for the speaker. As one of the other members said, do so cutting to fit them or exchange the speakers for a pair that is a bit shallower. I have used pioneer with out any issues.Does anyone know which speaker would fit in an 85 fleetwood? I bought new 4x6s for the front but they would not fit due to the speaker being too tall