Size of microphones in iphone 13 pro max

You can look at the specification sheet for iPhone 13 Pro Max, but I don't believe it's a specification which is listed:

Click here --> iPhone 13 Pro and 13 Pro Max - Technical Specifications - Apple

Other than what Apple publishes, no one could know if its not listed.

Size doesn't matter.

Were you asking about the speakers? The information you provided above would have more to do with speakers, not microphones.