dimensions of 10G cooler HLT w/sight glass

Through a complete miracle (or back luck?), I have two different sight glass assemblies from two different vendors with provisions for a thermometer heading my way. I'm only planning on using one of the two for my HLT that will be based on a home depot 10gallon round cooler.

Can anyone with a setup like this provide any tips on what kind of thermometer probe length I should be looking at? From what I can tell, the cooler wall is about 1.5", and based on pictures these fittings could be anywhere from 3"-4.5" from clearing the inside of the HLT to the outer side of the fitting beyond the sight glass.

Apparently the Blichmann brewmometers are too thick to fit in the bore, so I'm narrowing down to a Miljoco 3" dial type...I'm just stuck on the stem now whether 4" or 6" ...

I think you ought to wait. Install the systems and measure from there.

A 6" probe will give you 2.5" maybe into the cooler.

I measure it and its 2" without all the threads being tightened down.

Excellent- I realized after posting originally that I probably should have just asked you in the first place since that is exactly what I'm going to be using! Thanks!