Nickerbocker just asked this question in the recent Polini thread and wanted to make sure it got the right attention. For a while have been wondering the differences in size, etc between the Polini cylinders and haven't had much luck. Have a B cylinder from 1977 and curious if a C or D piston would would fit better if the cylinder is worn (miles of use), etc. Elliot mentioned that he is using a different piston than the one that came with his cylinder, but I can't remember or find what it was he said was the difference between the two. Anybody have the measurements or tried mis-matching them?