I have 5.25" in the front. All I did was make a special plate to go over the original plate area. You can fit 6.5" speaker in front, but it takes alot of work and you have to make sure the speaker is not to deep. I have 6.5" speakers in the rear and they fit in easly, only pain was geting the top top shelf off to get to them. No altercations to the door panals or rear deck.