To find the correct sizes, you should:
* Check your owner's manual: This is the best place to start. It might list the speaker sizes.
* Remove a speaker: The easiest way to know for sure is to remove one of your existing speakers and check the size. This will also allow you to see the mounting depth available. (Be careful when doing this; you might need specialized tools and be aware of the wiring.)
* Use an online resource: Several websites specialize in car audio. Search for "[year] [make] [model] speaker size" (e.g., "2002 Chevy Suburban speaker size") to find compatibility charts. These are often compiled by users and may contain inaccuracies, so use them with caution. Cross-reference multiple sources.
* Consult a car audio professional: A local car audio installer can quickly tell you the correct sizes.
Keep in mind that while you might find charts stating *standard* sizes, you may need to adapt or upgrade the mounting hardware to fit aftermarket speakers. Some aftermarket speakers require more depth than the factory speakers. Always check the specifications of any aftermarket speakers you consider buying to ensure they'll fit.