Quick question...What size speakers for our car?

[nitrox28]

1999 Firebird with the Monsoon system. I need to replace the speakers in the back seat so I thought I would just do the whole car. I've been hearing good things about Infinity and Polk. Will 6 1/2" or 6 3/4" fit the factory openings? Thanks.

[oneBADDz]

They say both will fit, most go with 6 1/2. You do have to watch the depth on the ones that go beside the back seats