UPDATE:
Made a slightly bigger version so that it would fit more snug inside the grommet. Re-did the flanges to make it bigger too. Printed it with PLA white for test fitting and eventually printed it out of ASA to put into my own car. Prints fine without supports with printed it with the tips down on the bed and a few lines of brim to keep it on the bed.
It's just a simple fitting with only one end that connects to ½" tubing and the other end is flush for a rubber grommet. You can buy these grommets from Amazon. They mainly sell it for hydroponic farms. I used one of these grommets and a ½" fitting for my custom intake piping. I didn't like how much the other end protruded inside the tube. So I just 3D modeled my own flush ½" fitting and used it.
Since this was going into a car, I printed it with ASA with no infill but ALL WALLS. It's a small fitting, don't bother printing infills. I also printed this at a speed of 50. Again, it's a small fitting. Don't print this too fast or it'll look and perform terribly. PLA will work fine if you're using this for a hydroponic farm. ASA recommended if it's going under the hood. No supports needed for the overhangs.
The author marked this model as their own original creation.