Thanks for the reply. You are correct the Parker size 2-007 5/32" id - 9-32 od 1/16 width or 3.68mm id 1.78mm width is not correct. I went back and remeasured the o-ring on my INON, Sea&Sea, Ikelite fiber optics and they are Parker size 2-006 1/8" 1/4" 1/16". What brand is your fiberoptic cables? The normal durometer is 70 but you can get a softer one, 50 durometer.
On a different subject, yes I understand that rocket science and o-rings are important. Please not that there are two different Bill's trying to provide help with your question. I never mentioned rocket science.