1/8" but would advise against it, as the system has been bled from all air bubbles in the factory, if you change the block you'll have the bleed the air from the loop but I don't see an easy way to to do this
Comment
from petersot@ 2008/07/18
Does anyone know if you can exchange the CPU block? What size are those hoses and if you cut the hoses, what happens? Can a person re-pressurize it?