Rodi pressure gauge size

[Rrb1399]

I need to get a new gauge the ones at homedepot threads are to big this is for an older triton model it connects to an elbow and threads in at the corner . Any idea what size it could be ?

 

[Biglew11]

Current ones are usually 1/4 npt, if thats to big then they are probably 1/8 npt.

 

[Rrb1399]

That’s what I was thinking