I believe they are 4"x6".
I got these and I an happy with them. I hear details in my music I never heard before.
These are the ones Crutchfield recommended. They said the rubber surround is more tolerant of sunlight.
KS Series 4"x6" 2-way car speakers
www.crutchfield.com
The front speakers in the dash are the same size. I have the 4x6 in the front and 4x10 in the rear. Don't do that! big mistake.
Long story
You'll need a Subwoofer to fill in the lows because 4x6's don't make a bunch of bass.
I have a Dual brand cheap powered 10"sub and I can hear the music clearly on the highway with the windows down.
The sub was given to me. I was going to get a powered 8" sub. That would have been enough.