What size comps can you put in the front of an A3?

[ReaperRCJS]

What size comps can you put in the front of an A3?
And what would you have to do to fit them? MDF rings? Ready made rings? straight into the door?

 

[AndyMac]

Stock units are 4" with a 1" tweeter. You can go up to 5.25" components but they need to be slim as you only have 55mm depth and that includes the adapter rings. You can buy crappy plastic ones for the A3 that don't fit properly or make your own from MDF. The MDF ones do use up more of the limited depth though.