1 way valve
thingiverse
Insert a 6mm airsoft BB and secure the cap tightly with a strong adhesive.
Download Model from thingiverse
With this file you will be able to print 1 way valve 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 1 way valve.