There are 2 versions of CT20b: steel and ceramic turbine.
The steel one can take more abuse.
Since it cannot be rebuilt easily (smaller shaft than a regular CT26), most people usually stay under 17 psi.
Have you looked into ATS's CT27 yet?
What are you talking about?!?!??!?! Who gives a shit what size it is. You know how much power it can put out and what it is capable of. Are you looking for some info so you can walk around saying... look how big my dick is??
Tell me how you determine the size of a turbo.... and I'll tell you how big the CT20B is.