hose diameter PCV - Breather - Catch Can

Hi,

maybe i´m starting a totally worthless discussion... but when searching the web and looking into engine bays of modern cars, i recon. that the hose diameter for PCV and/or Breather hoses or the plumbing for oil catch cans are vary from product to product...

this makes me thinink about: what is the minimum diameter e.g. when using an oil catch and having the PCV and Breather plugged to it.

btw... this should not be a discussion like "PCV needed or not.."