omission of "which are" - in letters two inches high

Question

His name was emblazoned across the headlines of the newspapers in letters two inches high.

Is "which are" omitted between "in letters" and "two inches high"?

And is "two inches high" an adjective phrase?

Answer 1

You could also insert that are or many other things. As it stands, this is perfectly normal/understandable to a native.