Does anyone know the size of the O-ring for the power brake vacuum line on a 1996 4.3 vortec?

I noticed a small hissing noise and have found it to be loose and not sealing properly. I have searched every possible combination of words for this and cannot find it on google.

It is the Engine side of the hose, the O-ring that is on the thing you twist to remove it from the intake.

Thanks!

 

Is this what you're looking for? It screws into the intake plenum on the driver side.

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