Rubber gaskets.

[ArdWrknTrk]

I have a combination of both those plastic ones and the rubbers. With the plastic I put sealant on the metal, put the plug in and smoothed out the squeeze out. Should be on my project page. With thos plastic ones they are tight, give them a good push in the middle and they will pop into place with good tactile feedback.

You could drill a hole in the middle of that plug put about a 1"long piece of clear tygon tubing from Lowe's through it (glued/sealed in) then run your coax through that tube. Once the coax is through tape both sides, then cut a slit just big enough for your sealant nozzle in one side and inject the tube with sealant. This will give you a good waterproof seal with a bit of reinforcement. May be overkill lol, you could also do a build up with some butyl tape.

You could probably just use Shoe-Goo.

It sticks tenaciously on cleaned surfaces, seals well and is available almost everywhere.

[Danny G]

You could probably just use Shoe-Goo.

It sticks tenaciously on cleaned surfaces, seals well and is available almost everywhere.

Yea that stuff is pretty incredible, there is a brand called "Goop" it has different versions but it seems all the same. E6000 is also good stuff in a similar category.

[ArdWrknTrk]

You could probably just use Shoe-Goo.

It sticks tenaciously on cleaned surfaces, seals well and is available almost everywhere.

Yea that stuff is pretty incredible, there is a brand called "Goop" it has different versions but it seems all the same. E6000 is also good stuff in a similar category.

4 or 5 kinds of Goop, and E6000.

All pretty much the same thing, marketed by the same company.

Steve83 has a manifesto on the stuff, if you care to search E6000.