I don't rememb er what size, but easy to remove, I replaced mine a few years ago with some really nice ones off eBay for much less than the local car stereo stores.. just pop the old one off and measure them... they weren't to hard to measure and repelace. the rear speakers were very hard to r and r because the rear window sits right on top of them..
Myabe the front ones were like 3 inch or so, but you better mearure them yourslef...
I think I got a set of real nice sound a set of 4 for maybe $50, but that was a few years back, the same set at like Circuit city wanted about $150.00 !
In the rear speakers slots I was able to place some 5 Inch speakers