6mm Tube
thingiverse
For those of you who do not want to buy hardware, here is a 6mm tube with a 0.8mm thickness, and 4 centimeters long. Note: you may have to sand the hole of the still a little bit to make it fit, but it should be a tight fit.
Download Model from thingiverse
With this file you will be able to print 6mm Tube with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on 6mm Tube.