The adapter exists in 2 variations : the normal version which has the thread, the grips and the connection to the tube as well as the "cocacola bottle to 10mm plastic tube with rubber seal" on which the thread hole is slightly deeper so we can fit a rubber seal like the one from a bottle as shown in the picture.  The adapter is not completely watertight  since it's 3d printed but it will do the job for normal applications unless you add too much pressure in which case it will start leaking a bit. I included the FreeCAD models so that you can modify the adapter and make it fit a different tube for example. PRINT SETTINGS : Material : PLA or PETG Orientation : vertical (thread on the bottom) Supports : enabled Infill : 50% (for optimal strength) Top and bottom layers : 5 NOTES : -The supports can be very tedious to remove from the thread but it's the only way to print the model in one part. -The model was made for flexible plastic tubes therefore the diameter of the top part is 11mm even though the tube inner diameter is only 10. If your tube isn't flexible enough, you might consider adjusting the values in the CAD model.