Ok gang I have learned from the original builder that the master cylinders came from C172, and could be McCauley or Cleveland depending on the year and whether the upgrade had been performed or not. Has anyone dealt with these style that look just like a Cleveland model 10-21 but have a plastic center and NO snap ring retainer. I just dont want to break them if I can help it, but they need new o-rings. Thanks in advance again, Colin N96TA