I popped a tripod adapter on these and am now nit-picking the water seal in this configuration. The photo may explain it better than I can, but the front cap is removed, and we have a recess in this bushing that leads to (what appears to be) an o-ring.
The black stud is flat against the silver bushing otherwise, but is not sealed with anything, just metal on metal.
O-ring should still do its job, but is probably at more risk of ultraviolet and chemical exposure, and I wonder if the cap was relied on to protect some of the components from direct flowing water. The little recess/notch may have a purpose, but the only one im aware of is to make sure their little bird logo stays oriented the right way.
Thoughts? The stud will come off if I need to, but didn't want to mess with removing/reaplying threadlocker.