@larryw posted:"I have found mine to be 25.4mm......."
That's an even inch. The ford and chevy masters that I have seen adapted are, I think, 15/16", or about 24mm, and the stock appearing style master is 23mm.
Is there an optimum size or is it about personal preference? Either the shorter throw and harder pedal of a larger bore, or easier pedal, but longer throw from the hydraulic advantage of a smaller bore?
I have both. As far as preference, I don't like the 1 1/8". There is less progression, and the pedal is much harder.