I have a 162mm Optar f4.5 and when I measure it I get about 1 3/4 or 44mm.
Is this the size I should be looking for? I bought a 45.5 and it seems really loose. I thought I could tweek it to fit, and I probably can but I would really rather have the right size without having to buy more that do not fit.
Thank you.

The series filter adapter should be the same size of the lens diameter. The adapter can be adjusted up to .5mm but the fingers may break off if pushed to the extreme.
The chart in this thread https://graflex.org/helpboard/viewtopic.php?t=3324
shows the 162mm Optar to use a 44.5mm series 7 filter adapter.