Oil pressure sensor o rings size

Anyone know what size this O ring is?

There are three o-rings used on the oil pressure switch ass'y (on most Zs:)
1 on the "Plug, oil pipe" P/N 670B2015 - 15mm]
1 under the "Oil Pipe" P/N 670B2018 - 18mm
1 on the oil pressure switch P/N 92055-055
(nil size given for this one in the IPB, but Partzilla and others give it as 19.5 X 1.5mm) - guess this is the one you need info on?

I was just thinking where sensor bolts to block. Guess I better check which one is leaking. I can tell that's where it's coming from but not sure which one it is.

More FYI .. Two of the O rings were 13mm and one was 5mm. Which isn't near what is shown on dealership computer or partzilla