Simple Question..

Just wondering what size all 4 speakers are on a 2000 F1

 

5x7,6x8

 

I assume by this one size really is the same as the other? I mean I could see where a 5x7 would fit in a 6x8. If they are the same size why do they call them the different sizes????? Makes a simple ole country boy like me go nuts trying to figure out if they really are different.