Disk inner diameter?

Hello-

What is the diameter of the inner hole on 3" and 4" disks?
And is the outer diameter of the disks EXACTLY 3" and 4"?

Thank You,
Bryan O.

3"...2-15/16" Od 1-5/8" Id
4"...3-2/3" Od 2-7/16 Id

Thanks for the info!
You ROCK!
It puts a hole new spin on a project I'm considering.

Thanks again,
Bryan O.