backs definately 6x4", fronts definately 3.5", not sure exactly about door ones as i don't have any i am afraid.
Some speakers don't fit as well as others - don't get infinity 6x4's as they don't line up with the mounting things properly. I sold mine and switched to JBL rear which went straight on.
The infity fronts fit with a little squeezing, think i filed a little off round the holes to get it in.. the pioneers i had previously fitted straight in no probs.