This is a grommet / pass through for feeding filament from a dry box, filament dryer, or elsewhere into a PTFE filament guide tube. It includes a pass through bolt with a tapered friction fit receiver for standard 4mm OD PTFE tubing, and a cap. I have also included the STL for TPU gaskets /washers, which help keep a good airtight seal. I've been using 6 of these for over a year now, 4 on a dry box, and another 2 on my filament dryer, and they've proven to be fully air tight and durable. I print a lot of TPU, which doesn't work in the AMS, so feeding directly from either my 4 spool dry box or my dryer makes things much easier, and helps keep my filament dry while printing. These are intended to be printed in PETG, and I have slowed the speed down slightly to help improve the quality of the threads. Due to tight tolerances the threads may be a bit tight the first time you thread the nut onto the bolt, but should work smoothly after that.

I will try to get around to publishing the rollers and silica holders that are the other part of my dry box setup using a Husky 5 gal watertight storage box. It's worked really well for me, and was pretty cheap and easy to build.