DIY ph probe fitting

[Isayso]

Hi all I'm very close to drill
My calcium reactor to install a ph probe,
But I threw out the old ph
Probe. So practically I don't have a proper size
Now I got
Compression fittings
That are 1/2" and 3/4"
They both have nitrile sleeves but which one is the right size?
https://flic.kr/p/2iwoyCD

https://flic.kr/p/2iwnoPX

 

[jrhupp]

Nominal size is 12mm diameter most of the pH probes used in the hobby. So, 1/2" is probably the right one.

 

[Isayso]

Thank you,
Also I forgot to ask
If the 1/2 is ok
Once I hit the sleeve on
Will It fit

 

[Isayso]

I guess that I have to do a dry fit before I start drilling the calcium reactor
Thanks again