Something like this? The blue tip is a grease needle tip for a grease gun. I drilled it out to fit a ball point pen refill cartridge. The other one uses a sharpie and a 3/8 npt female to 1/4 female brass adapter. On top of the sharpie in the pipe is a really light weight spring and a piece of all thread to limit how far the sharpie goes up into it, when THC comes down to the metal. Works really good. The outside of the galvanized pipe is 7/8" and the locking collars around the 1/8" pipe are 7/8" OD.
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